JPS6325245A - Filter glass for cutting near-infrared rays - Google Patents

Abstract

PURPOSE:The titled glass that is prepared by adding CuO, SiO2 and SnO2 to phosphate glass, thus showing improved chemical durability without reduced weathering and reduced transmission. CONSTITUTION:P2O5: 65-85wt%, Al2O3: 3-17wt%, SiO2: 0.1-12wt%, SnO2: 0.1-3wt% (SiO2+SnO2: 0.3-13wt%), B2O3: 0-10wt%, Li2O+Na2O+K2O: 0-15wt%, MgO+ZnO+CaO: 2-15wt%, BaO+SrO: 0-10wt%, ZrO2+TiO2+La2 O3+Y2O3: 0-10wt% and CuO: 1-8wt% are mixed, melted by heating at 1,000-1,400 deg.C in an oxidative atmosphere into a glass. Thus, a near-infrared ray-cutting filter glass which efficiently transmits the light in the visible range from 400-600nm and has good adsorption properties at 700nm wavelength is obtained. The glass is useful as a color-compensating filter for color VTR cameras.

Description

Detailed Description of the Invention [Object of the Invention] (Industrial Field of Application) The present invention is used for color correction filter glasses of color VTR cameras, etc., and efficiently transmits the visible range of 400 to 6001 m, and We are involved in near-infrared cut filter glass with good absorption characteristics.

(Prior Art) Conventionally, in an 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 11,000 nm, as shown by curve C in FIG. There is. Therefore, since it is not possible to obtain good color reproducibility as it is, it is necessary to correct the visibility to normal visibility (tJD) using a filter that absorbs the infrared region.

This filter selectively absorbs near-infrared wavelengths.
A filter glass made by adding CuO to phosphate glass is used. This filter glass contains a large amount of P2O and CuO as an essential component, and takes on a bluish-green color by forming Cu ions coordinated with many oxygen ions in an oxidizing bath melting atmosphere. Song N in Figure 1
It has near-infrared cut characteristics as shown in B.

However, when the content of CuO is increased in the above-mentioned filter glass to promote the near-infrared cut effect, the spectral transmittance in the wavelength range of 400 to 5000 m generally decreases and the glass tends to turn green. And 600-700 ri
Sharp cut characteristics in the m wavelength range deteriorate. 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 for 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
The object of the present invention is to provide a near-infrared cut filter glass that efficiently transmits a wavelength range of 600 nm, has good absorption characteristics at 7000 m, and has excellent chemical durability.

[Structure of the Invention] (Means and Effects for Solving the Problems) In order to achieve the above objects, the present invention provides 8 i Qz and S n
The basic glass composition was adjusted by adding No. 02. i.e. P2O565-85% by weight percentage
, A12033-17%, S r 020.1-12%
, S n 02-0.1-3%, 8 s 02 +S
n O20, 3-13%, B2030-10%, L+2
0+Na2O+K2O0~15%, MgO+ZnO+C
aO2~I 5%, BaO+SrOO~I 0%, Z
r 02 + T r 02 + La2O5, + Y2
The near-infrared cut filter glass has a composition of 0.030 to 10% and Cu of 01 to 8%.

The reason why the glass composition of the present invention is limited to the above range will be explained.

P2O5 is the main component that makes up the glass network, but it accounts for 65%
Below 400 nm, the transmittance decreases to 85%.
If it exceeds 100%, chemical durability deteriorates.

A-203 is an essential component for improving the chemical durability of glass, but if it is less than 3%, it will not be effective.
When it exceeds 17%, the transmittance in the ultraviolet region decreases and devitrification tends to occur. SiO□ and S n 02 have the effect of improving chemical durability, but SiO2 12%, S
If the total amount exceeds 13%, the infrared sharp cut characteristics will be inhibited by Cu ions, and devitrification will occur. B203Fi is an effective component for improving chemical durability and stabilizing glass, but if it exceeds 10%, the transmittance in the visible range decreases. Li2O, Na2O, 20
contributes to the stabilization of the glass, improves the transmittance in the wavelength range of 500 to 60011 m, and improves the near-infrared cut characteristics, but if it exceeds 15%, the chemical durability decreases, the viscosity of the glass decreases, and the rate of devitrification increases. becomes faster. MgO, ZnO.

If the total amount of one or more types of CaO is less than 2%, the moldability will deteriorate, and if it exceeds 15%, the infrared sharp cut property due to the CuO component will be inhibited.

BaQ and SrO act on Cu ions to increase the
The wavelength range of 0m is sharply cut, but the total amount is 10
%, devitrification occurs in the glass.

ZrO2+ 'l';02. Laz03, Y2O
3 is a component that improves chemical durability without affecting near-infrared sharp cut;
When the content of m exceeds 10%, the glass has devitrification.

CuO is added as a colorant 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 experience weathering in high-humidity environments, and their transmittance properties decrease due to surface scattering of light.However, the glass of the present invention reduces weathering and improves its transmittance properties by adding the 8nO□ component. We were able to reduce the decline in

(Example) Examples of the present invention are 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.

All of Omote Maefu's glasses are made by mixing raw materials to obtain a predetermined oxide composition, melting at a temperature of 1000 to 1400 degrees Celsius at Rutsuho, stirring and fining, casting into molds, slowly cooling, and then cutting. , obtained by polishing. If Cu ions are reduced during melting, desired spectral transmission characteristics cannot be achieved, so melting and refining were performed in an oxidizing atmosphere.

The spectral transmittance characteristics of the glass of the present invention are shown in FIG.

In the figure, curve A is the characteristic curve of the example KL8 glass, and curve B is the characteristic curve of the comparative example Al4 glass.

〔Effect of the invention〕

As described above, the glass of the present invention has CuO in phosphate glass.
In the near-infrared cut filter glass doped with Si
Contains up to 13% of O□ and S n 02 in total, improving chemical durability, which was considered a drawback in the past, and efficiently transmitting visible light from 400 to 600 nm, with absorption at 700 nm. This has the advantage of improving characteristics.

[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.

Claims (1)

[Claims] In weight percentage, P_2O_565-85%, Al_2O
_33-17%, SiO_20.1-12%, SnO_
20.1-3%, SiO_2+SnO_20.3-13
%, B_2O_30-10%, Li_2O+Na_2O
+K_2O0~15%, MgO+ZnO+CaO2~1
5%, BaO+SrO0~10%, ZrO_2+TiO
_2+La_2O_3+Y_2O_30~10%, Cu
A near-infrared cut filter glass having a composition of 1 to 8% O.