JPS62153144A - Near infrared cutting filter glass and production thereof - Google Patents

Abstract

PURPOSE:To improve the chemical durability, by reducing the contents of alkali metal oxides to a specific amount or less and blending one or two or more or ZrO2, La2O3 and Y2O3 and an adequate amount of SO3 in near infrared cutting filter glass containing CuO added to phosphate glass. CONSTITUTION:The composition of near infrared cutting filter glass is adjusted as follows; 65-85wt% P2O5, 5-17wt% Al2O3, 2-12wt% total of MgO, ZnO and CaO, 2-10wt% total of BaO and SrO, 0.2-10wt% B2O3, SiO2, ZrO2, TiO2, La2O3 and Y2O3, <1wt% SO3 and 0.5-8wt% CuO. Raw materials are mixed to give the above-mentioned composition and 1-10wt% SO3 as a sulfate is contained in the raw materials. The resultant raw materials are melted to afford the aimed near infrared cutting filter glass.

Description

Detailed Description of the Invention [Technical Field of the Invention] The present invention is used for color correction filters of color VTR cameras, etc., and efficiently transmits the visible range of 400 to eoonm and sharpens the wavelength range of 600 to 700 nm. This invention relates to a near-infrared cut filter glass to be cut and a method for manufacturing the same.

[Technical background of the invention and its problems]

The photosensitive element of the image pickup tube used in a color VTR camera is looped from the visible range as shown by curve C in Figure 2.
It has spectral sensitivity over the near-infrared region around m. Therefore, since good color reproduction cannot be obtained as is, a filter that absorbs infrared light is used to correct the visibility to normal visibility (curve D).

This filter selectively absorbs near-infrared wavelengths.
A filter glass made by adding CuO to phosphate glass is used. This glass contains a large amount of P20T5 and CuO as an essential component, and in an oxidizing molten atmosphere, Cu2+ ions coordinated with many oxygen ions form, giving it a blue-green color, as shown in Figure 1. It has near-infrared cut characteristics as shown by curve B.

However, when the above-mentioned filter glass increases the CaO content to promote the near-infrared cut effect, the spectral transmittance in the 400 to 500 nm range generally decreases and the glass tends to turn green, and the spectral transmittance in the 600 to 7 QQ nm range generally decreases. Sharp cut characteristics deteriorate. In addition, since the base glass is phosphate glass, its weather resistance is insufficient and weathering occurs on the polished surface of the glass, making it difficult to use for a long period of time, so it is desirable to improve its chemical durability. ing.

[Purpose of the invention]

The present invention was made in consideration of the above circumstances, and
(Efficiently transmits the wavelength range of 3QQnm,
It is an object of the present invention to provide a near-infrared cut filter glass having good sharp cut characteristics at 0 nm and excellent chemical durability, and a method for producing the same.

[Summary of the invention]

In order to achieve the above object, the present invention has an alkali metal oxide content of 0.2% by weight or less, and the composition of the base glass is adjusted. i.e. P2O in weight percentage
1165-85%, AltOn 5-17%, MgO
+ ZnO+ CaO2~12%, BaO+ SrO2
~lO%, BzOa+SiO2+Zr0z+Ti1t+
It is a near-infrared cut filter glass having a composition of L820a+YzQa 0.2 to 10%, SOa 1% or less, and CuO 0.5 to 8%.

In addition, the raw materials are mixed to obtain the above glass composition,
This is a method for producing near-infrared cut filter glass in which 1 to 10% by weight of SOa is contained as a sulfate in raw materials and melted.

CuO is added as a coloring agent and is an essential component for near-infrared sharp cutting.

P2O5 is the main component constituting the glass network, and A11
zOs is an essential component to improve the chemical durability of phosphate glass. MgO, ZnO1CaO.

BadlSrO is a glass network modifying oxide and is a component for improving solubility and moldability and preventing devitrification.

B2O3, SiO2, Zr0z, TiO2, L atO
s, Y, 0. is a component that improves chemical durability without affecting near-infrared sharp cut.

SOa is a component that is introduced by selecting raw materials for alkali metals, alkaline earth metals, and copper and converting them into sulfates, and improves chemical durability. Also, sulfate Mn So
4 (Mn' alkali metal, alkaline earth metal, or copper) undergoes a chemical reaction during the melting process, forming MnSO4-
'MnO+Sos, 5os-+soz+o, and the generated oxygen 0 keeps the melting glass strongly oxidized, promoting the coloring of Cu2+ ions and exhibiting a remarkable effect on the sharp cutting property of near-infrared rays.

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

When P20!1 is less than 6596, the transmittance at 400 nm decreases, and when it exceeds 85%, the chemical durability of the phosphate glass deteriorates. If All to S is less than 5%, the chemical durability will decrease, and if it exceeds 17%, the transmittance in the ultraviolet region will decrease and the meltability will change.

If the content of one or more of MgO, ZnO, and CaO is less than 2%, the chemical durability will decrease and the formation IF21f will decrease.
l: Introducing Gawa A (-12%) inhibits the infrared sharp cut performance of CoO. If Bad or SrO is used alone or if the content is less than 296, good near-infrared sharp cutting performance cannot be obtained, and if it exceeds 10%, devitrification occurs in the glass.

B 203.5iO-1ZrO2, Ti0-1La20
3. When the total amount of one or more of Y2Q3 exceeds 10%, the glass has devitrification properties and deteriorates the near-infrared sharp cut performance.

If SO3 exceeds 1%, absorption in the visible region increases, which is not preferable.

When CaO is less than 0.596, a good near-infrared sharp cutting effect cannot be obtained, and when it exceeds 8%, the transmittance in the entire visible range decreases.

Since Na2O and K2O5Li20 reduce chemical durability, it is desirable not to include them, but their inclusion as impurities in other raw materials is unavoidable, so they are allowed up to 0.2%.

Next, in the glass manufacturing method of the present invention, the reason why the amount of Son contained as a sulfate in the raw materials is limited to 1 to 10% by weight will be explained.

If the amount of SOa introduced as sulfate is less than 1%, a decomposition reaction will occur during the melting process and there will be little effect in maintaining the oxidizing atmosphere, and if it exceeds 10%, foaming will occur significantly during melting.
It overflows from the crucible, making it difficult to melt. In addition, there are many bubbles remaining in the glass.

By containing 1-10% by weight of SO3, SOs remains until the melting is completed in the glass of the present invention,
It maintains an oxidizing atmosphere, improves the near-infrared sharp cutting property of CuO, and improves the water resistance of glass.

[Embodiments of the invention]

Examples of the present invention are shown in the following table. In the table, Nα1 to Nα9 are examples, Nα10 to Nα12 are comparative examples, and the glass compositions are shown in weight percentages. Water resistance is determined by the method for measuring chemical durability of optical glass as specified by the Japan Optical Glass Industry Association. .

(Left below) All the glasses in the previous table are made by weighing and mixing the raw materials to obtain the specified oxide composition, and heating them in a crucible at 1,100 to 1,400°C.
It is obtained by melting at a temperature of 100 ml, stirring, clarifying, casting into a mold, slowly cooling, cutting and polishing.

If Cu ions were reduced during melting, desired spectral transmission characteristics could not be achieved, so melting and refining were performed in an oxidizing atmosphere.

Examples Nα1 to Nα9 glasses have a weight loss rate of 0.01% or less in water resistance, fully complying with the value of less than 0.05% for class 1 of the Japan Optical Glass Industry Association standards, and are shown to have excellent water resistance. Is recognized. The spectral transmittance characteristics of Example Nα4 glass and Comparative Example Nα11 glass are shown in curves A and B in FIG. 1, respectively. The glass of the present invention also has better characteristics than conventional products in terms of near-infrared sharp cut property and transmittance at wavelengths of 400 to 5QQnm.

Next, in the glass manufacturing method of the present invention, 8% of SO8 is introduced into a predetermined mixed raw material and melted at 1400°C for 5 hours, and the glass contains 0.02% of S03.
Glass containing 5% of SOa and melted at 1300° C. for 2 hours contains 0.05% of SOa. In addition, S in the raw material
The glass containing 1.596% of O3 and melted at 1100° C. for 6 hours contains 0.0596% of S08. All of these glasses exhibit excellent near-infrared sharp cutting properties and water resistance.

〔Effect of the invention〕

As described above, the glass of the present invention has phosphorus and CuO in the glass.
In the near-infrared cut filter glass doped with Na
201, the content of alkali metal oxides such as 01Li and O is suppressed to 0.296 or less, and ZrO2, Ti02Laz
It contains one or more of Oa, Y2O3, and SO3 in appropriate amounts, has the advantage of improving chemical durability, and efficiently transmits the visible range of 400 to 3QQ nm, and It has an excellent effect of sharply cutting the wavelength range of ~70Qnm.

[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 Nα4), B...
... Conventional glass (comparative example Nα11). Patent applicant: Toshiba Glass Corporation Figure 1 Wavelength (nm) Wavelength (nm)

Claims (2)

[Claims] (1) P_2O_5 65-85% by weight percentage, Al
_2O_3 5-17%, MgO+ZnO+CaO2
~12%, BaO+SrO 2~10%, B_2O_3
+SiO_2+ZrO_2+TiO_2+La_2O_
A near-infrared cut filter glass having a composition of 3+Y_2O_3 0.2 to 10%, SO_3 1% or less, and CuO 0.5 to 8%. (2) P_2O_5 65-85% by weight percentage, Al
_2O_3 5-17%, MgO+ZnO+CaO2
~12%, BaO+SrO 2~10%, B_2O_3
+SiO_2+ZrO_2+TiO_2+La_2O_
3+Y_2O_3 0.2-10%, SO_3 1% or less, CuO 0.5-8%, and the raw materials are mixed with 1-1% SO_3 as sulfate.
A method for producing near-infrared cut filter glass containing 10% by weight and melting.