JPH02204342A - Near infrared absorption filter glass - Google Patents

Abstract

PURPOSE:To provide the above filter glass which has a high transmittance in a visible region and has the stable characteristics unaffected by the fluctuation in the conditions of a melting stage by incorporating an oxide selected from As2O3, Sb2O3 and CeO2 into CuO-fluorophosphate base glass. CONSTITUTION:The effective ratios of at least one kind selected from the group consisting of the As2O3, the Sb2O3 and the CeO2 are incorporated into the CuO-fluorophosphate base glass contg. CuO 0.2 to 15wt.% based on the total weight of P2O5 and metal fluoride to form the near IR absorption filter glass which has the excellent transmittance at 400 to 520nm and is adequate for color correction, etc., of a color VTR camera. The effective ratios of the respective components are 0.005 to 5 parts in the case of the As2O3, 0.005 to 3 parts in the case of the Sb2O3 and 0.01 to 1 part in the case of the CeO2 per 100 pts.wt. the base glass. These effects are highest with the As2O3, and are decreased successively by the Sb2O3 and the CeO2 in this order.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a fluorophosphate-based near-infrared absorption filter glass suitable for use in color correction of color VTR cameras, etc.

[Background technology] -The spectral sensitivity of the light from the image pickup tube used in color VTR cameras extends from the visible region to the near-infrared region of 950 nm, so this near-infrared region is cut with a filter to reduce the spectral sensitivity. If we don't shortsight human visibility,
The image becomes reddish and good color reproduction cannot be obtained. On the other hand, if the absorption of the ultraviolet side of the filter used extends into the visible range, the image will become darker. Therefore, this kind of filter has 400
~520nm light transmittance is as high as possible, 550~
A property that absorbs as much light as possible at 950 nm is required. Conventionally, as this type of near-infrared absorbing filter, glass obtained by adding CuO to phosphate glass has been used.

However, since phosphate glass originally has poor weather resistance, in order to improve it to a point where it can withstand practical use, it is necessary to add a relatively large amount of Al2O3, as disclosed in Japanese Patent Publication No. 128943/1983. I need. As a result, the melting temperature rises, and the higher the temperature, the more easily copper is reduced, so the divalent copper ions Cu2+ in the glass component, which absorbs in the near-infrared region, are reduced and absorb in the ultraviolet region. There was a tendency for characteristic deterioration in which the transmittance in the visible region became low and the transmittance in the infrared region increased. On the other hand, when trying to improve the transmittance characteristics, divalent copper ions Cu in the glass component
In order to prevent 2+ from being reduced to monovalent ions Cu, the melting temperature is lowered by adding an alkali or the like, but at the same time this further deteriorates the weather resistance of the glass itself. Therefore, when producing this type of near-infrared absorbing filter using phosphate glass, the reality is that a compromise between transmittance characteristics and weather resistance, which are contradictory to each other, has to be found and provided for practical use. Conventionally, it has been impossible to satisfy both heat resistance properties and excellent weather resistance at the same time.

In view of these circumstances, the present inventor developed a near-infrared absorbing filter glass made by adding CuO to fluorophosphate glass as a glass that simultaneously satisfies the transmittance characteristics and weather resistance required for filters for color VTR cameras. Heading: A patent application has been filed for this near-infrared absorbing filter glass (Japanese Patent Application No. 47118/1983). This CuO-fluorophosphate glass is a useful glass having far superior transmittance characteristics and weather resistance compared to conventional phosphate glasses, and can be put to practical use.

[Problems to be Solved by the Invention] However, like conventional phosphate glasses, the transmittance of this CuO-fluorophosphate glass changes in the 400 to 520 nm range due to changes in melting conditions such as temperature and atmosphere during the melting process. However, in some cases, the desired high transmittance cannot be obtained.

[Means for solving the problem] As a result of intensive research aimed at reducing the variation in transmittance due to changes in melting conditions and further improving the transmittance at 400 to 52011 ffl,
Effective L of As203 for CuO-fluorophosphate base glass
．． It was discovered that the above object could be achieved by adding 5b203 and CeO2, and the present invention was completed.

That is, the near-infrared absorbing filter glass of the present invention has Cu
O-fluorophosphate base glass, A S 203, S
b203 and CeO2 in an effective amount.

The present invention will be explained in detail below.

The CuO-fluorophosphate base glass used in the near-infrared absorbing filter glass of the present invention is manufactured by applying the Patent application 63-47 related to a person's earlier application
It is preferable to use the CuO-fluorophosphate glass described in No. 118.

This Cu0-fluorophosphate glass has a weight of 5 to 45
% P2O5: 1-35% AlF3; 10-75% RF2 (R is Ba, Sr, Ca.

at least one divalent metal selected from the group consisting of Mg, Zn and pb); 0 to 40% R' F (R
' is at least one monovalent metal selected from the group consisting of Li, Na, and K); and 0 to 15% R''Fm
(R” is La, Y, Gd.

at least one trivalent to pentavalent metal selected from the group consisting of St, B, Zr, and Ta, where m is a number corresponding to the valence of the metal R'' (provided that the metal fluoride (up to 70% by weight of P2O5 can be replaced by metal oxide), and further 0.2% based on the total combined weight of the above-mentioned P2O5, metal fluoride and optionally substituted metal oxide.
It contains ~15% CuO.

However, the CuO-fluorophosphate base glass used in the present invention is not limited to that described in the above-mentioned Japanese Patent Application No. 63-47118.

The near-infrared absorbing filter glass of the present invention has Al2O3゜5b203 and C
e O2 contains an effective amount of at least one selected from the group consisting of O2.

"Effective amount" here refers to the above As203.5b203,
This means the amount of CeO2 that can contribute to suppressing transmittance fluctuations and improving transmittance without causing any adverse effects due to these additions, and the effective amount when these are used alone is Cu
For 100 parts by weight of O-fluorophosphate base glass, AS2
In the case of 03, 0°005 to 5 parts by weight, in the case of S b 203, 0.005 to 3 parts by weight, and in the case of CeO2, 0.0
It is preferable to use 1 to 1 part by weight because As2
03°S b 203 and Ce 02 are each 0.
If the amount is less than 0.005 parts by weight, 0.005 parts by weight, or 0.01 parts by weight, there is little effect on suppressing transmittance fluctuations and improving transmittance at 400 to 5200 m.
s2 o3. When Sb203 exceeds 5 parts by weight and 3 parts by weight, respectively, unmelted substances are likely to occur in the glass, and when Ce02 exceeds 1 part by weight, the effect of absorption in the ultraviolet region of CeO7 itself becomes strong, resulting in 400~ This is because it becomes impossible to improve the transmittance at 520 nm.

However, the above addition amount range of As2 o3, 5l) 203 and CeO2 is a tentative standard, and depending on the composition of the CuO-fluorophosphate base glass, etc., As2
O3,5b203. The object of the present invention may also be achieved when CeO2 is added.

As203.5b203, the effect of CeO2 is
03 has the highest value, followed by S b 203 and CeO2.

Furthermore, a mixture of two or more types of As203, Sb203, and CeO2 may be used within the range of 0.005 to 5 parts by weight.

The near-infrared absorbing filter glass of the present invention is prepared by mixing predetermined amounts of commonly used raw materials such as oxides, phosphates, carbonates, and fluorides, placing the mixture in a platinum crucible with a lid, and heating the mixture to 800 to 1000°C.
It is obtained by melting, stirring, defoaming, and homogenizing, then casting into a preheated mold and slowly cooling.

[Example] The present invention will be further explained below with reference to Examples.

Example 1 On a weight basis, P2O527.8%, AlF38°2%,
MgF25.3%, CaF210.4%.

5rF219.4%, BaF215.0%.

This basic glass 100 was added to the CuO-fluorophosphate base glass (corresponding to composition N08A in Table 1) containing 107.9% A, 6.0% Li2O, and 1.4% CuO based on the total weight of the above components. AS2031 for each part by weight
Parts by weight, 2031 parts by weight of S b and 20.2 parts by weight of CeO were added (composition No. 1.2 in Table 1).
．． 3) was melted at 850°C for 35 minutes and polished to a glass thickness of 1.0 mm. Composition No. 1°2.
The results of measuring the spectral transmittance of the glass sample No. 3 are shown in FIG. 1 together with the spectral transmittance of the base glass of composition No. A.

From Figure 1, the glass sample with composition No. 1.2.3 has improved transmittance from 400 to 520 nm than the base glass with composition No. A, and the effect of the addition of As2O3°SbOCeO2 is recognized2. 3. Rena.

Example 2 On a weight basis, P2O523.0%, AlF38°9%,
MgF24.0%, CaF211, 4%.

BaF234.4%, LiF5.3%, KF5゜0%,
Contains A12 o35.0%, Li2O3,0%,
CuO- containing 51% CuO based on the total weight of the above components
Fluorophosphate basic glass (corresponds to composition No. and B in Table 1)
AS for each 100 parts by weight of this basic glass.
2031 parts by weight, Sb2031 parts by weight, Ce 020
, 2 parts by weight were added (composition No. in Table 1).
, corresponding to 4.56) at 950° C. for 35 minutes and polished to a glass thickness of 3 mm. Composition No.

The results of measuring the spectral transmittance of the glass sample No. 4.5.6 are shown in FIG. 2 together with the spectral transmittance of the base glass of composition No. B.

From Figure 2, the transmittance of the glass sample with composition No. 4.5.6 is improved by 400 to 520 nlll compared to the basic glass with composition No. B, and As2 o3 ° Sb O, C
No effect was observed due to the addition of eO2.

Example 3 In order to see the effect of melting temperature, a base glass composition of composition No. A and a composition of composition No. 1 in which As2O3 was added were melted at 950° C. for 35 minutes to obtain a glass thickness of 1. The spectral transmittance of the sample polished to .0ml was measured. As is clear from Figure 3, the results are as follows:
In the case of composition No. A, the transmittance greatly decreases due to the increase in melting temperature, whereas in the case of composition No. 051, the transmittance hardly decreases even if the melting temperature increases, and As2O3
When you add it, it melts! ! It became clear that there was little variation in transmittance due to temperature variation.

Example 4 In order to examine the influence of the melting atmosphere, a composition was prepared in which 6.0 parts by weight of the 5.0 parts by weight of BaF2 L in the basic glass composition of composition No. A was replaced with B a CO3 (composition N in Table 1).
01C) and A92031 to 100 parts by weight of this composition No. C.

0 parts by weight of the composition (composition No. in Table 1).

7), the spectral transmittance of a sample obtained by melting the glass at 850° C. for 35 minutes and polishing it to a glass thickness of 1 mm was measured. As shown in Figure 4, the results show that in the case of composition No. C, the transmittance is greatly reduced due to the carbon dioxide atmosphere, while in the case of composition No. 17, the transmittance is decreased due to carbon dioxide gas. is hardly seen, and A
It has become clear that when S203 is added, the transmittance changes less due to changes in the melting atmosphere.

Example 5 As2 was added to 100 parts by weight of the basic glass composition of composition No. A.
Results of measuring the spectral transmittance of a sample obtained by melting a glass obtained by melting it under the same conditions as in Example 1 and polishing the glass to a glass thickness of 1 mm for a composition to which 2 parts by weight of o3o and 2030,01 parts by weight of 5b were added. , 400-5 as in Example 1
An improvement in transmittance at 200 m was observed.

(The following is a blank space) [Effects of the invention] As stated above, a predetermined amount of A S 203 and S b
The near-infrared absorbing filter glass of the present invention, which is made of CuO-fluorophosphate glass containing 203 and Ce02, has a higher transmittance in the wavelength range of 400 to 520 nm and is not affected by changes in conditions during the melting process. It is possible to obtain difficult and stable characteristics and is useful not only for color VTR cameras but also for color print filters and the like.

[Brief explanation of the drawing]

FIG. 1, FIG. 2, FIG. 3, and FIG. 4 are graphs showing the spectral transmittance of the near-infrared absorbing filter glass of the present invention.

Claims (1)

[Claims] (1) A near-infrared absorption filter glass characterized by containing an effective amount of at least one member selected from the group consisting of As_2O_3, Sb_2O_3 and CeO_2 in a CuO-fluorophosphate base glass.