US20080132402A1 - Optical glass - Google Patents

Optical glass Download PDF

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Publication number
US20080132402A1
US20080132402A1 US11/616,716 US61671606A US2008132402A1 US 20080132402 A1 US20080132402 A1 US 20080132402A1 US 61671606 A US61671606 A US 61671606A US 2008132402 A1 US2008132402 A1 US 2008132402A1
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US
United States
Prior art keywords
optical glass
wavelength
glass
less
amount
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Abandoned
Application number
US11/616,716
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English (en)
Inventor
Tomohiro Watanabe
Taihei Mukaide
Hidenosuke Itoh
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Canon Inc
Original Assignee
Canon Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Canon Inc filed Critical Canon Inc
Assigned to CANON KABUSHIKI KAISHA reassignment CANON KABUSHIKI KAISHA ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: ITOH, HIDENOSUKE, MUKAIDE, TAIHEI, WATANABE, TOMOHIRO
Priority to US11/932,024 priority Critical patent/US7727918B2/en
Publication of US20080132402A1 publication Critical patent/US20080132402A1/en
Abandoned legal-status Critical Current

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
    • C03C4/00—Compositions for glass with special properties
    • C03C4/0085—Compositions for glass with special properties for UV-transmitting glass
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B19/00—Other methods of shaping glass
    • C03B19/14—Other methods of shaping glass by gas- or vapour- phase reaction processes
    • C03B19/1415—Reactant delivery systems
    • C03B19/1438—Reactant delivery systems for delivering and depositing additional reactants as liquids or solutions, e.g. solution doping of the article or deposit
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
    • C03C3/00—Glass compositions
    • C03C3/04—Glass compositions containing silica
    • C03C3/076—Glass compositions containing silica with 40% to 90% silica, by weight
    • C03C3/083—Glass compositions containing silica with 40% to 90% silica, by weight containing aluminium oxide or an iron compound
    • C03C3/085—Glass compositions containing silica with 40% to 90% silica, by weight containing aluminium oxide or an iron compound containing an oxide of a divalent metal
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B2201/00—Type of glass produced
    • C03B2201/06—Doped silica-based glasses
    • C03B2201/07—Impurity concentration specified
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B2201/00—Type of glass produced
    • C03B2201/06—Doped silica-based glasses
    • C03B2201/20—Doped silica-based glasses doped with non-metals other than boron or fluorine
    • C03B2201/23—Doped silica-based glasses doped with non-metals other than boron or fluorine doped with hydroxyl groups
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T428/00—Stock material or miscellaneous articles
    • Y10T428/26—Web or sheet containing structurally defined element or component, the element or component having a specified physical dimension
    • Y10T428/261—In terms of molecular thickness or light wave length

Definitions

  • the present invention relates to an optical glass used in an apparatus including a light source emitting ultraviolet (UV) rays or vacuum UV rays, particularly an optical glass used as an optical component, such as a lens, a prism, or a window member, in regions from UV rays such as that (wavelength: 248 nm) of a KrF excimer laser to vacuum UV rays.
  • a light source emitting ultraviolet (UV) rays or vacuum UV rays particularly an optical glass used as an optical component, such as a lens, a prism, or a window member, in regions from UV rays such as that (wavelength: 248 nm) of a KrF excimer laser to vacuum UV rays.
  • a conventional optical component such as a lens, a prism, or a window member, used in an apparatus employing light ranging from UV rays to vacuum UV rays
  • Synthetic quartz glass is transparent to light in a wide wavelength region from a near-infrared region to a vacuum UV region and its transmittance to a light having a wavelength of 157 nm is 95% at a thickness of 1 cm.
  • Fluorite is transparent to a light having a shorter wavelength than synthetic quartz glass and has a transmittance to the light having the wavelength of 157 nm of 99% or more at a thickness of 10 mm.
  • Japanese Laid-Open Patent Application 2001-64038 has disclosed a glass material comprising SiO 2 , Al 2 O 3 , B 2 O 3 , and CaO and containing iron in an amount of 50 ppm or less.
  • This glass material is principally used for carrying a photocatalyst used in a photocatalyst filter or the like and is required to improve a UV-ray transmitting characteristic at a wavelength of 365 nm.
  • a transmittance in a wavelength range of approximately 310-410 nm is improved by using a high-purity starting material, preventing impurity contamination in the glass material production process, and employing a reducing agent.
  • An action of the reducing agent is to reduce an Fe 3+ ion having an adsorption peak at a wavelength of approximately 365 nm to an Fe 2+ ion having an absorption peak at a wavelength of approximately 850 nm.
  • a refractive index at a wavelength of 248 nm is 1.51 and 1.47 for synthetic quartz glass and fluorite, respectively, which have been used in the conventional exposure apparatus.
  • fluorite which is a crystal, has an intrinsic birefringence problem.
  • the MgO single-crystal has a refractive index of about 1.82 at a wavelength of 248 nm.
  • the MgAl 2 O 4 single-crystal has a refractive index of about 1.77. Therefore, these materials have sufficient refractive indices for an optical member for a UV wavelength region.
  • the MgO single-crystal has a transmittance of about 18% at a thickness of 9 mm
  • the MgAl 2 O 4 single-crystal has a transmittance of about 80% at a thickness of 3.4 mm
  • the MgAl 2 O 4 polycrystal has a transmittance of about 72% at a thickness of 2.7 mm.
  • the MgO single-crystal has an intrinsic birefringence value of 16.0 ⁇ 0.5 nm/cm (extrapolation value) and MgAl 2 O 4 single-crystal has an intrinsic birefringence value of 14.6 ⁇ 0.1 nm/cm (extrapolation value), thus providing much larger values than that ( ⁇ 0.55 ⁇ 0.07 nm/cm) of CaF 2 .
  • a content of iron in the glass material is 50 ppm or less in order to improve the transmittance to UV rays having a wavelength of 365 nm.
  • the Fe content in glass is 1.0 ppm and Si containing 0.1 ppm of an impurity as a reducing agent is used in an amount of 0.01 wt. %
  • a transmittance at a wavelength of approximately 248 nm is about 50% at a thickness of 1 mm. In this case, however, the glass material used does not have a sufficient refractive index.
  • a principal object of the present invention is to provide an optical glass, which has a high refractive index and a high transmittance and which causes no intrinsic birefringence in a UV region.
  • an optical glass that comprises SiO 2 and Al 2 O 3 and to which MgO is added is effective.
  • an optical glass comprising Si, Al, Mg, and O,
  • optical glass contains Si in an amount of 40% or more and 60% or less, in cation percent, Al in an amount of 10% or more and 95% or less, in cation percent, and Mg in an amount of 20% or more and 35% or less, in cation percent, a total amount of Si, Al, and Mg being 99.5% or more, in cation percent, and
  • the optical glass contains Fe and Na each in an amount of 0.01 wtppm or less and has a transmittance to a light having a wavelength of 248 nm of 40% or more at a thickness of 5 mm.
  • the above-described optical glass may preferably contain an OH group in an amount of 5000 wtppm or less.
  • the above-described optical glass may preferably have a refractive index to a light having a wavelength of 248 nm of 1.57 or more.
  • an optical glass having a high refractive index and a high transmittance in a UV region.
  • FIG. 1 is a graph showing wavelength dependence of a refractive index of the optical glass according to the embodiment of the present invention.
  • FIG. 2 is a graph showing wavelength dependence of a transmittance of an optical glass according to the embodiment of the present invention.
  • the optical glass according to the present invention has a higher refractive index and a higher transmittance in a UV wavelength region compared with synthetic quartz glass and fluorite.
  • n a refractive index
  • Eg a band gap (eV).
  • a fluorine-containing material such as fluorite, has a large band gap, so that it is highly transparent to light of short wavelengths.
  • a fluoride ion has a smaller electronic polarizability (1.04 ⁇ 10 ⁇ 24 cm 3 ) than that (3.88 ⁇ 10 ⁇ 24 cm 3 ) of an oxide ion, so that the fluorine-containing material is undesirable in terms of the high refractive index.
  • synthetic quartz glass has a refractive index of 1.51 and fluorite has a refractive index of 1.47.
  • the above-described SiO 2 —Al 2 O 3 —MgO-based glass has a refractive index of 1.57 at the wavelength of 248 nm.
  • the optical glass according to the present invention is Si—Al—Mg—O based glass comprising Si, Al, Mg, and O,
  • optical glass contains Si in an amount of 40% or more and 60% or less, in cation percent, Al in an amount of 10% or more and 95% or less, in cation percent, and Mg in an amount of 20% or more and 35% or less, in cation percent, a total amount of Si, Al, and Mg being 99.5% or more, in cation percent, and
  • the optical glass contains Fe and Na each in an amount of 0.01 wtppm or less and has a transmittance to a light having a wavelength of 248 nm of 40% or more at a thickness of 5 mm.
  • the optical glass according to the present invention contains Si.
  • An amount of Si (Si content) contained in the optical glass according to the present invention is 40% or more and 60% or less, preferably 45% or more and 55% or less, in terms of cation %.
  • a cation % of Si means a ratio of the ion number of a cation of Si to the sum of the ion numbers of the cations of Si, Al, and Mg, on a percentage basis.
  • a cation % of Al means a ratio of the ion number of a cation of Al to the sum of the ion numbers of the cations of Si, Al, and Mg, on a percentage basis.
  • a cation % of Mg means a ratio of the ion number of a cation of Mg to the sum of the ion number of the cations of Si, Al, and Mg, on a percentage basis.
  • SiO 2 is capable of forming glass by itself and is a frequently used glass component. As described above, SiO 2 has a band gap (Eg) of about 9 eV, so that it exhibits excellent optical transparency and light resistance with respect to UV rays and vacuum UV rays. A refractive index thereof is 1.51 at a wavelength of 248 nm, which is small. Accordingly, Si content may preferably be increased in order to permit transmission of light of short wavelengths, but the increase in Si content is disadvantageous with respect to the improvement in refractive index. Further, when the Si content is larger, a resultant material is liable to vitrify and has a small thermal expansion coefficient, thus being improved in stability as glass. However, viscosity and melting points thereof are increased.
  • the Si content in accordance with the present invention may be in the above-described range.
  • the optical glass in the present invention contains Al.
  • An amount of Al (Al content) contained in the optical glass according to the first aspect of the present invention is 10% or more and 35% or less, preferably 12% or more and 33% or less, in terms of cation %.
  • Al 2 O 3 is a glass component for improving chemical durability that is added to a so-called glass-forming oxide, such as SiO 2 or the like. Further, Al 2 O 3 has a band gap (Eg) of 8.7 eV as described above and high optical transparency with respect to UV rays and vacuum UV rays. Further, compared with SiO 2 , Al 2 O 3 improves the refractive index, so that Al content in accordance with the present invention is preferably in the above-described range.
  • the optical glass in the present invention contains Mg.
  • An amount of Mg (Mg content) contained in the optical glass according to the present invention is 20% or more and 35% or less, preferably 22% or more and 33% or less, in terms of cation %.
  • MgO functions as a so-called modifier oxide in glass formation to decrease the viscosity.
  • MgO has an Eg of 7.6 eV, so that MgO has a larger band gap (Eg) than energy (5.0 eV) of a KrF excimer laser (wavelength: 248 nm).
  • Eg band gap
  • MgO is treated as an impurity, which decreases transparency to UV rays.
  • Mg—O has a binding energy of 88 kcal/mol, which is smaller than that (150 kcal/mol) of SiO 2 and that (115 kcal/mol) of Al 2 O 3 , thus resulting in low bond strength. Therefore, it is preferable to increase the MgO content from the viewpoint of improvement in the refractive index. However, it is preferable to decrease the MgO content from the viewpoint of increasing optical transparency and light resistance with respect to UV rays and vacuum UV rays. Therefore, the Mg content in accordance with the present invention is preferably in the above
  • each of Fe and Na is contained in an amount of 0.01 wtppm or less, preferably 0.001 wtppm or less.
  • wtppm means a weight ratio of Fe or Na to the entire weight of optical glass.
  • the optical glass according to the present invention is an optical member formed of glass, so that similar to synthetic quartz glass and fluorite that have been employed for the same purpose, it is preferable for the optical glass to contain as little impurity as possible having an absorption peak in UV region. More specifically, it is required in the present invention that high-purity starting materials be used and impurity contamination during the production process be reduced as much as possible.
  • Oxides of metal elements examples of which may include oxides of transition metals, such as Ti or Fe, and oxides of alkali metal, such as Na or K, are principal impurities of UV and vacuum UV transmissive materials. It is desirable for these oxides to be substantially excluded from the optical glass of the present invention. Furthermore, it is desirable to substantially exclude from the optical glass of the present invention other metal oxides having band gaps close to or lower than the UV or vacuum UV energy to be used.
  • the optical glasses according to the present invention it is desirable for the optical glasses according to the present invention to contain not more than 5000 wtppm, preferably 2000 wtppm or less, of an OH group.
  • the OH group is present close to Mg and accelerates the destabilization of the network structure of glass. This results in a decrease in light resistance to UV rays or vacuum UV rays. For this reason, the OH group content is preferably as low as possible.
  • the optical glass of the present invention may desirably have a transmittance to a light having a wavelength of 248 nm of 40% or more, preferably 50% or more, at a thickness of 5 mm.
  • the optical glass of the present invention has a refractive index to a light having a wavelength of 248 nm of 1.57 or more.
  • a process capable of eliminating impurity contamination is preferable. More specifically, examples of such a process may include a process in which starting materials are melted by electricity, arc plasma, or flame; a flame hydrolysis procedure; a direct process; a soot remelting process, such as vapor-phase axial deposition (VAD) or modified chemical vapor deposition (MCVD); plasma CVD; sol-gel process; and the like. In any process, it is preferable to use high-purity starting materials.
  • VAD vapor-phase axial deposition
  • MCVD modified chemical vapor deposition
  • sol-gel process sol-gel process
  • the soot of SiO 2 was synthesized in a glass vessel of SiO 2 by a CVD apparatus to obtain A.
  • the thus synthesized A was immersed in a solution of AlCl 3 hydrate (purity: 99.9999% or more) and MgCl 2 hydrate (purity: 99.9999% or more) in ultrapure water and then was dried for about 12 hours in a dry nitrogen gas atmosphere to obtain B.
  • the thus obtained B was heated at about 2300° C. from the outside of the glass vessel by means of an oxy-hydrogen burner to melt B, followed by cooling to obtain an optical glass (material).
  • the thus obtained glass was in a melted state together with the glass vessel, so that a central portion was cut and optically polished to obtain a parallel flat plate having a thickness of about 5 mm.
  • the OH group concentration (content) is expected to be about 17000 wtppm.
  • the transmittance of the glass was measured by a visible-ultraviolet spectrophotometer.
  • the refractive index of the glass was measured by a fast spectroscopic ellipsometer (“M-2000D”, mfd. by J. A. Woolam Co., Inc.).
  • FIG. 1 shows a wavelength dependence of the refractive index of the glass obtained in this Example.
  • FIG. 2 shows a wavelength dependence of the external transmittance of the glass obtained in this Example.
  • the measured transmittance at a wavelength of 248 nm was 43%.
  • the measured refractive index at a wavelength of 248 nm was 1.57.
  • An optical glass was prepared in the same manner as in Example 1, except that the drying time for preparing the powder B was changed to 3 hours.
  • the OH group content was about 1500 wtppm.
  • the measured transmittance was 38%.
  • the optical glass has a high refractive index and high transmittance in a UV region, so that it is possible to use the optical glass as an optical part, such as a lens, a prism, a window material, and the like, in a wavelength range from UV rays to vacuum UV rays.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Materials Engineering (AREA)
  • Organic Chemistry (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • General Chemical & Material Sciences (AREA)
  • Geochemistry & Mineralogy (AREA)
  • Manufacturing & Machinery (AREA)
  • Glass Compositions (AREA)
US11/616,716 2006-12-05 2006-12-27 Optical glass Abandoned US20080132402A1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
US11/932,024 US7727918B2 (en) 2006-12-05 2007-10-31 Optical glass

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP2006328745A JP2008143718A (ja) 2006-12-05 2006-12-05 光学ガラス
JP328745/2006(PAT.) 2006-12-05

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20080131691A1 (en) * 2006-12-05 2008-06-05 Canon Kabushiki Kaisha Optical glass

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4664473A (en) * 1985-04-01 1987-05-12 Corning Glass Works Optical fiber formed of MgO--Al2 O3 --SiO2 glass
US5099174A (en) * 1988-07-12 1992-03-24 Thorn Emi Plc Arc tube for a discharge lamp
US6645891B2 (en) * 2000-04-03 2003-11-11 Minolta Co., Ltd. Glass composition for crystallized glass
US20040138044A1 (en) * 2002-12-25 2004-07-15 Nippon Sheet Glass Company Limited Glass composition for poling and glass functional product containing the same
US7291571B2 (en) * 2002-09-27 2007-11-06 Schott Ag Crystallizable glass and the use thereof for producing extremely solid and break resistant glass-ceramics having an easily polished surface
US20080131691A1 (en) * 2006-12-05 2008-06-05 Canon Kabushiki Kaisha Optical glass
US20080227616A1 (en) * 2004-01-05 2008-09-18 Ulrich Peuchert Use of Glass Ceramics

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2001064038A (ja) 1999-08-30 2001-03-13 Hoya Corp ガラス材およびそれを用いたガラスファイバ
JP4614403B2 (ja) * 2000-10-13 2011-01-19 信越石英株式会社 プラズマ耐食性ガラス部材
DE10362074B4 (de) * 2003-10-14 2007-12-06 Schott Ag Hochschmelzendes Glas oder Glaskeramik sowie der Verwendung
JP2008143719A (ja) * 2006-12-05 2008-06-26 Canon Inc 光学ガラス

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4664473A (en) * 1985-04-01 1987-05-12 Corning Glass Works Optical fiber formed of MgO--Al2 O3 --SiO2 glass
US5099174A (en) * 1988-07-12 1992-03-24 Thorn Emi Plc Arc tube for a discharge lamp
US6645891B2 (en) * 2000-04-03 2003-11-11 Minolta Co., Ltd. Glass composition for crystallized glass
US7291571B2 (en) * 2002-09-27 2007-11-06 Schott Ag Crystallizable glass and the use thereof for producing extremely solid and break resistant glass-ceramics having an easily polished surface
US20040138044A1 (en) * 2002-12-25 2004-07-15 Nippon Sheet Glass Company Limited Glass composition for poling and glass functional product containing the same
US20080227616A1 (en) * 2004-01-05 2008-09-18 Ulrich Peuchert Use of Glass Ceramics
US20080131691A1 (en) * 2006-12-05 2008-06-05 Canon Kabushiki Kaisha Optical glass

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20080131691A1 (en) * 2006-12-05 2008-06-05 Canon Kabushiki Kaisha Optical glass
US7727918B2 (en) * 2006-12-05 2010-06-01 Canon Kabushiki Kaisha Optical glass

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JP2008143718A (ja) 2008-06-26
US7727918B2 (en) 2010-06-01
US20080131691A1 (en) 2008-06-05

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Owner name: CANON KABUSHIKI KAISHA, JAPAN

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:WATANABE, TOMOHIRO;MUKAIDE, TAIHEI;ITOH, HIDENOSUKE;REEL/FRAME:018832/0013

Effective date: 20070124

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