JPH0393648A - Ultraviolet ray transmitting glass - Google Patents

Abstract

PURPOSE:To obtain optical glass having a high transmittance within an ultraviolet region with hardly any deterioration in the transmittance due to irradiation with ultraviolet rays by melting glass with a limited component composition and containing specific amounts of especially SiO2, B2O2, La2O3 and PbO added thereto and forming the resultant melt. CONSTITUTION:Ultraviolet ray transmitting glass prepared by melting glass having the following composition. The aforementioned composition is 2-25wt.% SiO2, 10-30wt.% B2O3, 9-50wt.% La2O3, 2-10wt.% PbO, 0-40wt.% BaO, 0-10wt.% MgO, 0-15wt.% CaO, 0-10wt.% SrO, 0-25wt.% ZnO, 0-10wt.% ZrO2, 0-5wt.% Al2O3, 0-10wt.% Gd2O3, 0-10wt.% Y2O3, 0-5wt.% Nb2O5, 0-10wt.% Ta2O5, <3ppm Fe, <3ppm Cr and <0.2wt.% reducing additive, in which the total content of Fe, Cr and other transition metals is lower than 3ppm.

Description

[Detailed description of the invention] Industrial applications The present invention relates to ultraviolet tSS overglass.

In recent years, optical glass has been used for ultraviolet photography lenses (used for archeology, police identification, etc.), ultraviolet erasing EFROM window glass, and optical systems that use mercury lamps as a light source. transmits shorter wavelength light with higher efficiency,
A UV-transmitting glass with excellent solarization resistance is desired.

In particular, reduction projection lenses used in steppers have a thick core and a large number of lenses.
It is required that the internal transmittance is >95% in the ultraviolet region and that the transmittance does not deteriorate due to ultraviolet irradiation (solarization resistance).

In addition, conventional ultraviolet-transmitting glass has a refractive index of less than 1.55 for the d-line, but in ultraviolet optical systems such as reduction projection lenses, a higher refractive index is required to correct chromatic aberration. There is a need for high-speed optical glass.

Ultraviolet-transmitting glass is described in Japanese Patent Publication No. 54-36164: B @O @-S io *-L ago s-Z r
Compositions of o-divalent metal oxides and SnO. A reduction technique is disclosed by introducing the transmittance λT80>3
65 nm (glass thickness 10+++a transmission wavelength); JP-A-55-3329: Compositions of BtOs-SiOt-LatOs-YbtOs and SnO. A reduction technique by introducing the is disclosed.

Transmittance λT80> 3 6 5 nm (glass thickness 10 m
m transmission wavelength) has been achieved; Japanese Patent Publication No. 55-37500 and Japanese Patent Publication No. 56-40
Publication No. 094 includes P. O. A composition of the system is disclosed, with a transmittance λT80 > 3 6 5 nm (glass thickness 10
Ils transmission wavelength) has been achieved; JP-A-58-13
Publication No. 0136: A p20s-TatOs-based composition is disclosed, and a transmittance λToo > 3 6 5 nm (transmission wavelength with a glass thickness of 10 mm) is achieved; JP-A-60-46946: s, os -S10w-AhOs A CaO-based composition is disclosed, and it is stated that FetOs is <0.03% by weight and that a small amount of a reducing agent may be included.

Thickness 3. 6 mm, the transmittance at λ=25.7 nm is about 69%; JP-A-60-77-144: B. 03-Sin,-NatO-Al2tOs series composition is disclosed, F2.5-10% by weight, Sn
There is a description of reduction by O. The thickness is 1 mm, and the transmittance at λ=253.7 nm is 80-85%; JP-A-60-200842: S10w-Btus-'-AQtOs-RtO and F
*Glass having a porous antireflection film (surface treatment) consisting of 0.1 to 6% by weight of the composition is disclosed; JP-A-60-215547: SiO1 Al2tOs Btus CaO
HgO BaO and Fe10s < 10
A composition comprising 0 ppm is disclosed. Transmittance=8
0% has been achieved; Unexamined Japanese Patent Publication No. 1986-1-20 1640
Publication: S 10y Btus AQ*Os N
a=O-(CaO+HgO+ZnO)-NiO-Coo
JP-A No. 62-27346 discloses a composition of PtOs SiO*-AmO; JP-A No. 62-65951: P*O s B 10 s A12tO s and Nip < 15% by weight, Coo < 15% by weight; JP-A-62-87433: Composed of SiO1-B103-BaO, Fe and other transition metals < i ppm compositions are disclosed.

Transmittance λT80=300 to 320 (glass thickness 10 mm transmission wavelength) has been achieved; JP-A-62-153142: Sins B*Oa Al2! O-RtO
Composition consisting of RO and reducing agents carbon, tartaric acid, S
There is a description of using i, AI2. Thickness 1mm, λ=
A transmittance of 75% at 253.7 nm has been achieved; JP-A-63-11544: A composition of Pro@Lat03 LitO is disclosed; JP-A-63-265840: S10w Btus Pros TiO1 N
b*Os(ZnO+PbO)(LLO+Na*O+K
tO) is disclosed, and the transmittance λT8G>
420 has been achieved; JP-A-63-282-139: Siot-AfftOs-BtOs-NatO-(L
t20 kyO) BaO (As=O, +sb*
os) NtO-CoO composition; etc. are known; however, the composition system and the method for achieving high transmittance in the ultraviolet region are different from the present invention, and the method for improving the transmittance is further improved. is desired.

Also, J, Non-Cryst. Solids l 0
7 (1989), p. 30, 3 using high-purity raw materials.
Although a component alkaline earth-metaphosphate glass is disclosed, the component system is different from the present invention, and the transmittance λT50 (thickness I
OIII1, wavelength of 50% transmittance) = 195 to 300n
It is l.

Problems to be Solved by the Invention The present invention provides an optical glass that has high transmittance in the ultraviolet region and that does not (or has very little) deterioration in transmittance due to ultraviolet irradiation, more specifically, has an Abpe number νd of 37.
~50, the refractive index nd is 1.67 to 1.79, and the wavelength at which a transmittance of 80% or more is obtained with a thickness of 10 mm is 36
An object of the present invention is to provide an optical glass having a diameter of 5 nm or less.

Means for Solving the Problems That is, the present invention provides a highly UV-transparent glass with excellent solarization resistance, which is produced by melting a glass having the following composition: SiOt B2O, La. o. PbO BaO MgO CaO SrO ZnO ZrO, 2-25% by weight 10-30% by weight 9-50% by weight 2-10% by weight 0-40% by weight 0-10% by weight 0-15% by weight 0-10% by weight 0- 25% by weight 0-10% by weight A Q x O s 0-5% by weight Gd
tes 0-10% by weight Y2O.
0~10wt% NbtOs 0~
5% by weight Ta*0,3 o~10% by weight
Fe < 3 ppmCr
<3ppm Reducing additives <0.2% by weight (however, F
content of e, Cr and other transition metals is less than 3 ppm).

The glass produced in this manner also has good solarization resistance.

In general, the main causes of absorption in the ultraviolet region of glass are (1) many transition metal ions such as Fe34 and Cr@◆ in the glass (2) platinum dissolved in the glass (if the melting crucible is platinum) ) (3) There is fundamental absorption in the ultraviolet region due to the glass structure.

On the other hand, the wavelength used for UV-transparent glass is approximately 2
It is around 50 to 440no+, and the absorption due to the above (3) is thought to be on the shorter wavelength side than this wavelength, and as long as a component without absorption is used as a glass component, 250
The absorption around ~440no+ seems to be mainly due to (1) and (2). In particular, the absorption wavelength of Fe3+ or Cr●◆ in (1) is 380 nm for Fe3◆, C
r'' is 350 n+s, and the absorption coefficient is large, so even if a small amount is mixed in, the transmittance will deteriorate.

In the present invention, the valence state of iron and chromium is F.
If it is a low atomic state of e'', Cr'', its absorption wavelength is Fe'': 1 0 5 0ne% Cr34'' = 43
This is to take advantage of the fact that it is on-feng.

If the content of Sin is less than 2% by weight (hereinafter referred to as wt%), the volatilization of B*Oa becomes intense, making striae more likely to occur, and chemical durability deteriorates. Also, Si
n. When the content is more than 25 wt%, the melting temperature becomes high, the glass viscosity becomes high, and the meltability deteriorates.

When the content of B t O s is less than 15 wt%,
The liquidus temperature becomes high, and if the amount exceeds 30 wt%, volatilization becomes intense and striae are likely to occur.

La. O. is a part that makes the glass have a high refractive index and low dispersion, and is necessary to achieve the optical performance targeted by the present invention, and also appropriately lowers the glass viscosity.
It also acts as a melting aid. La. The content of O is 9wt.
Even if it is less than 50wt, these functions will not be sufficient.
%, the liquidus temperature becomes high.

PbO makes the glass have a high refractive index and high dispersion, and lowers the viscosity of the glass, and also works as a melting aid for Sins. If the content of PbO is less than 2 wt%, these functions will not be sufficient, and if it is more than 10 wt%, the liquidus temperature will become high.

BadSMgOSCaO and SrO are effective in suppressing the tendency to devitrify;
5wt% and. If it exceeds 1Qwt%, the chemical durability will deteriorate or, conversely, the tendency to devitrify will increase.

ZnO is effective in improving meltability, but if it exceeds 25 wt%, it actually worsens.

ZrO* is effective in improving chemical durability, but 10
If it exceeds wt%, the tendency to devitrify increases.

AQ*Os is effective in suppressing phase separation and improving chemical durability, but if it exceeds 5 wt%, it increases the viscosity of the glass.

Gd. O, and Y t O- are components that make the glass high in refractive index and low in dispersion;
If it exceeds t%, the liquidus temperature becomes high and the tendency to devitrify increases.

Nb. O. is a component that makes the glass have a high refractive index and high dispersion and suppresses the tendency to devitrify, but if it exceeds 5 wt%, the transmittance of the glass in the ultraviolet region deteriorates.

Ta*Os is a component that provides high refractive index and low dispersion, and contributes to improving chemical durability and stability of glass.
Since Ta*Os is expensive, if it is contained in excess of 8 wt%, the cost of the glass will increase.

Reducing additives include Si, C, etc., and these substances reduce impurities (iron, chromium, etc.) mixed in raw materials and processes (crucibles) to a low valence state, and reduce transmission in the ultraviolet region. It works to improve the rate. Their usage is 0.2
The amount is up to wt%, and for St it is 0. Amounts up to 1% by weight are preferred. If 0.2 wt % or more of reducing substances are used, those substances remain in the glass as unmelted substances, and conversely cause deterioration of ultraviolet transmittance.

Fe" and cr" are components that greatly deteriorate the transmittance in the ultraviolet region, and their absorption numbers are large, so Fe and C
The content of r is 3 ppm+ or less.

FeSCr and other transition metals (e.g. M n ,
The total amount of Nf, Co), etc. should be 3 ppm or less from the viewpoint of deterioration of transmittance in the ultraviolet region.

The production of optical glass involves melting glass raw materials (powder) once,
The molten material obtained by mixing may be poured into a desired mold and cooled to solidify. Another method is to roughly melt the glass raw material (powder) to once produce cullet (glass particles), and then finish melting to match the optical constants.

In the case of the former manufacturing method, a crucible made of highly pure ceramics is used. In the case of the latter manufacturing method, it is also preferable to use a high-purity ceramic crucible for the rough melting, and to use a high-purity platinum crucible in a neutral or reducing atmosphere for the final melting.

The reason why high-purity ceramics are used in this way is that since the present invention uses a reducing agent, it is difficult to use a platinum crucible for rough melting.

High-purity ceramic crucibles are made of materials such as quartz, alumina, and carbon, and impurities in these materials
e<3 pptr, Cr<3 PpI% The content of other transition metals (e.g. (Mn, Ni, Co) etc. is 3 p
Use one that is pm. Use of such a crucible is effective in preventing Fe, Cr, etc. from being mixed into the glass composition.

As the high-purity platinum-gold crucible, it is preferable to use one containing the same impurities and amounts as the above-mentioned high-purity ceramic crucible. The reason for using such high purity platinum is the same as the reason for using a high purity ceramic crucible.

Although it is possible to melt the glass lens under a normal air atmosphere, it is useful to perform the melting under a neutral or reducing atmosphere.

Melting in a neutral atmosphere is Fe”◆ in a low valence state.
, Cr34" is effective in preventing it from becoming highly atomized (Fe"◆, Cr"◆: absorption in the ultraviolet region), and such an atmosphere uses an inert gas such as Ar, N*, etc. This is possible by doing the following.

Melting under a reducing atmosphere produces a high valence state (1;'
es +Cr”+, etc.) to a low valence state (Fe snow◆, Cr
3◆), and also reduces the low valence state of Fe”, Cr”+ to the high atomic state (Fe3+, Cr
It is also effective in preventing @+). Such an atmosphere can be obtained by mixing about 5% by volume of a reducing gas such as H8 or CO with an inert gas such as Nfis Ar.

It has been found that when the ultraviolet-transmitting glass of the present invention is produced throughout the entire process in a neutral atmosphere or a reducing atmosphere, the addition of a reducing agent is not necessarily necessary, and even in that case, the object of the present invention can be achieved. .

Herein, the present invention provides a highly UV-transmissive glass having excellent solarization resistance and produced by melting the following glass; S i O *B. O, L a, o , PbO BaO MgO CaO SrO ZnO ZrO* 1'-Q*Os Gd*Os Y x O s Nb20. Tagos Fe Cr 2-25% by weight 10-30% by weight 9-50% by weight 2-10% by weight 0-40% by weight 0-10% by weight 0-15% by weight 0-10% by weight 0-25% by weight 0-10% by weight 0-5% by weight 0-10% by weight 0-10% by weight 0-5% by weight 0-10% by weight <3 ppg+ <3 ppm (However, the content of Fe, Cr and other transition metals is less than 3 ppm).

Non-oxidizing atmosphere means the above-mentioned neutral atmosphere or reducing atmosphere.

Using only the reduction method produces more Fe″ than not using it.
It is possible to actively shift the redox equilibrium of medium → Fe", Cr"-*Cr'◆ toward the reduced state Fe", Cr34", and relatively reduce the total amount of iron and total chromium mixed in the glass. The proportion of Fe'' and Cr'◆ can be increased.

For this purpose, it is preferable to use high-purity raw materials with as few impurities (iron, chromium, etc.) as possible, and to use a high-purity ceramic crucible or platinum crucible as described above as the glass melting crucible.

The present invention will be explained below with reference to Examples.

An ultraviolet transmitting glass having excellent solarization resistance according to the present invention was produced under the composition and conditions shown in Tables 1 and 2 as follows.

Note that the total amount of Fe, Cr, and other transition metals in the glass raw material was 3 ppm or less.

(1) One-time melting The numbers 1 to 11 at the top of Table 1 indicate examples in which glass was produced by one-time melting.

Glass compositions shown in Table 1 were produced by melting 100 g of glass in a quartz crucible at a temperature of 1250 to 1350°C, stirring, pouring into a preheated mold, and slowly cooling.

(2) Twice melting In table 1, the numbers 1-R-11-R at the top indicate examples in which glass was produced by melting twice.

The second melting used a non-oxidizing atmosphere during melting. The glass is made by melting and stirring the same type of glass used in (1) above in a platinum crucible at a temperature of 1200 to 1300°C in a non-oxidizing atmosphere, then casting it into a preheated mold, and slowly cooling it. Manufactured by

(3) Atmosphere In Table 1, the numbers 1-E-1 1-E at the top indicate examples in which no reducing agent was used and a non-oxidizing atmosphere was used. Table 1
The glass composition shown in 100g of glass is platinum,
It was manufactured by melting quartz, alumina, and carbon at a temperature of 1250 to 1350°C in a non-oxidizing atmosphere in a crucible, stirring, pouring into a preheated mold, molding, and slow cooling.

As comparative examples, R-1 and R-2 are shown in Table 1.

In addition, each raw material in the table includes carbonate, nitrate,
and appropriate compounds such as oxides were used.

In each table, λT80 indicates the wavelength at which the transmittance is 80% based on the spectral transmittance curve of a sample having a thickness of 10 mg+ and mirror-polished with parallel surfaces, based on the standards of the Japan Optical Glass Industry Association. λ'780 is determined based on the same standard.
OW 30mm away from the high pressure mercury lamp, irradiated for 3 hours, 2
It was measured in the same manner as λT80 after 0 minutes.

In the atmosphere column, N2 is nitrogen, Ar is argon, H2 is 9
5% nitrogen + 5% hydrogen, CO represents 95% nitrogen + 5% carbon monoxide, respectively.

Also, the value of (nd-1) is (nd-1) the value of $10,000 Effect of the Invention The ultraviolet transmitting glass of the present invention has a high ultraviolet transmittance.
Excellent UV deterioration resistance.

Claims (1)

[Claims] 1. High ultraviolet transmittance glass with excellent solarization resistance produced by melting glass with the following composition; SiO_22-2
5 weight% B_2O_3 10-30 weight% La_2O_39-50 weight% PbO2-10 weight% BaO 0-40 weight% MgO 0-10 weight% CaO 0-15 weight% SrO 0-10 weight% ZnO 0-25 weight% ZrO_20-10 weight% Al_2O_30~ 5% by weight Gd_2O_30-10% by weight Y_2O_30-10% by weight Nb_2O_50-5% by weight Ta_2O_50-10% by weight Fe<3ppm Cr<3ppm Reducing additives<0.2% by weight However, Fe, Cr and other transition metals The content is 3
Less than ppm. 2. The reducing additive is Si, and the amount added is Si<0
．． 2. The glass of claim 1, wherein the amount is 1% by weight. 3. The reducing additive is C, and the amount added is C<0.2
% by weight of the glass according to claim 1. 4. The glass according to claims 1 to 3, wherein the crucible used for melting is high-purity quartz, alumina, platinum, and carbon. 5. The amount of impurities in the crucible during melting is Fe<3ppm
, Cr<3ppm, and content of other transition metals<3
The crucible according to claim 4, wherein the amount is ppm. 6. The glass according to any one of claims 1 to 5, wherein the melting comprises rough melting and remelting, and the remelting is performed in a high purity platinum crucible. 7. The crucible according to claim 6, wherein the high purity platinum has a purity of Fe<3ppm, Cr<3ppm and content of other transition metals<3ppm. 8. Remelting in a neutral atmosphere of Ar and N_2 or N
7. The glass according to claim 1, wherein the glass treatment is carried out in a reducing atmosphere of _2+5% H_2 and N_2+5% CO. 9. High UV transmittance glass with excellent solarization resistance made by melting glass with the following composition; SiO_22~2
5 weight% B_2O_3 10-30 weight% La_2O_39-50 weight% PbO2-10 weight% BaO 0-40 weight% MgO 0-10 weight% CaO 0-15 weight% SrO 0-10 weight% ZnO 0-25 weight% ZrO_20-10 weight% Al_2O_30~ 5% by weight Gd_2O_30-10% by weight Y_2O_30-10% by weight Nb_2O_50-5% by weight Ta_2O_50-10% by weight Fe<3ppm Cr<3ppm However, the content of Fe, Cr and other transition metals is 3
Less than ppm. 10. The glass according to claim 9, wherein the non-oxidizing atmosphere is a neutral atmosphere of Ar and N_2. 11. The glass according to claim 9, wherein the non-oxidizing atmosphere is a reducing atmosphere of N_2 + 5% H_2 and N_2 + 5% CO. 12. The crucible used for melting is made of high purity quartz, alumina,
The glass according to claim 9, which is platinum and carbon. 13. The amount of impurities in the crucible during melting is Fe<3pp
m, Cr<3ppm, and content of other transition metals<
13. The crucible according to claim 12, wherein the concentration is 3 ppm.