WO2013146378A1 - 光学ガラスおよびその利用 - Google Patents
光学ガラスおよびその利用 Download PDFInfo
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- WO2013146378A1 WO2013146378A1 PCT/JP2013/057496 JP2013057496W WO2013146378A1 WO 2013146378 A1 WO2013146378 A1 WO 2013146378A1 JP 2013057496 W JP2013057496 W JP 2013057496W WO 2013146378 A1 WO2013146378 A1 WO 2013146378A1
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- 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
- C03C3/062—Glass compositions containing silica with less than 40% silica by weight
- C03C3/064—Glass compositions containing silica with less than 40% silica by weight containing boron
- C03C3/068—Glass compositions containing silica with less than 40% silica by weight containing boron containing rare earths
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- 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
- C03C3/095—Glass compositions containing silica with 40% to 90% silica, by weight containing rare earths
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- 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
- C03C3/12—Silica-free oxide glass compositions
- C03C3/14—Silica-free oxide glass compositions containing boron
- C03C3/15—Silica-free oxide glass compositions containing boron containing rare earths
- C03C3/155—Silica-free oxide glass compositions containing boron containing rare earths containing zirconium, titanium, tantalum or niobium
Definitions
- the present invention relates to an optical glass having a high refractive index and a low dispersion property, a glass gob for press molding made of the optical glass, an optical element blank, and an optical element.
- a lens made of high refractive index and low dispersion glass can be combined with a lens made of ultra low dispersion glass to make the optical system compact while correcting chromatic aberration. Therefore, it occupies a very important position as an optical element constituting a projection optical system such as an imaging optical system or a projector.
- An example of such a high refractive index and low dispersion glass is HOYA Corporation optical glass (glass type TAFD25 (refractive index nd 1.90366, Abbe number ⁇ d 31) described in OPTICAL GLASS Technical Data 2011 (published by HOYA Corporation). .32)).
- optical glass which is a lens material
- glass that is particularly desirable for chromatic aberration correction has high refractive index and low dispersion
- the optical glass TAFD 25 is a very excellent glass material that is very low in coloring while being a high refractive index and low dispersion glass.
- ⁇ Pg, F is 0.0028, and in order to correct higher-order chromatic aberration, an optical glass having a smaller ⁇ Pg, F is desired.
- high refractive index and low dispersion glass is disclosed in JP-A-60-131845 or English family member US Pat. No. 4,584,279, US2011 / 0028300A1, JP2010-083705 or English family member US2012 / 0142517A1.
- U.S. Pat. No. 8,127,570 the entire description of which is also incorporated herein by reference.
- One embodiment of the present invention provides an optical glass having high refractive index and low dispersion characteristics and suitable for high-order chromatic aberration correction, a glass gob for press molding made of the glass, an optical element blank, and an optical element.
- the present inventor has intensively studied to make the glass component a glass network forming component (Si 4+ , B 3+ ), a high refractive index low dispersion component having a function of increasing the refractive index while maintaining low dispersion. (La 3+ , Gd 3+ , Y 3+ , Yb 3+ ), high refractive index / high dispersion component (Ti 4+ , Nb 5+ , W 6+ , Bi 3 ) that works to increase both refractive index and dispersion.
- the content of the network forming component, the content of the high refractive index and low dispersion component, the high refractive index and high dispersion By adjusting the ratio of the content of the high refractive index and low dispersion component and the content of the high refractive index and high dispersion component and adjusting the overall composition, Optical glass with low refractive index and low dispersion characteristics and suitable for high-order chromatic aberration correction is obtained. Newly found to be.
- the total content of Si 4+ and B 3+ is in the range of 10-60 cation%
- the total content of La 3+ , Gd 3+ , Y 3+ and Yb 3+ ranges from 25 to 70 cation%
- the total content of Ti 4+ , Nb 5+ , W 6+ and Bi 3+ is in the range of 10-20 cation%
- Li + content is in the range of 0-5.0 cation%
- the Ge content is less than 5.0% by weight as GeO 2 in the oxide-based glass composition; Does not contain Pb
- the cation ratio of the Si 4+ content to the B 3+ content (Si 4+ / B 3+ ) is 0.70 or less, Cation ratio of the total content of La 3+ , Gd 3+ , Y 3+ and Yb 3+ to the total content of Ti 4+ , Nb 5+ , W 6+ and Bi 3+ ((La 3+ + Gd 3+ + Y 3+ + Yb 3+ )
- the Yb content of the optical glass is less than 2% by mass as the amount of Yb 2 O 3 in the oxide-based glass composition.
- the cation ratio of the total content of La 3+ , Gd 3+ , Y 3+ and Yb 3+ to the total content of Si 4+ and B 3+ in the optical glass [(La 3+ + Gd 3+ + Y 3+ + Yb 3+ ) / (Si 4+ + B 3+ )] is 0.83 or more, or Ti 4+ , Nb 5+ , W 6 with respect to the total content of Si 4+ and B 3+
- the cation ratio [(Ti 4+ + Nb 5+ + W 6+ + Bi 3+ ) / (Si 4+ + B 3+ )] of the total content of + and Bi 3+ is 0.31 or more.
- the total content of Ti 4+ , Nb 5+ , W 6+ , Bi 3+ and Ta 5+ in the optical glass is in the range of 13-30 cation%.
- the Si 4+ content of the optical glass is in the range of 1-30 cation%
- the B 3+ content is in the range of 5-55 cation%
- the La 3+ content is 10-50%. It is in the range of cation%.
- the optical glass has a Zr 4+ content in the range of 1 to 15 cation%.
- the optical glass has a Zn 2+ content in the range of 0 to 15 cation%.
- the glass transition temperature of the optical glass is greater than 630 ° C.
- the total content of Gd 3+ , Y 3+ and Yb 3+ in the optical glass ranges from 0.5 to 35 cation%.
- a further aspect of the invention provides: In cation% display, 10 to 60% in total of Si 4+ and B 3+ La 3+ , Gd 3+ , Y 3+ and Yb 3+ in total 25 to 70%, 10 to 20% in total of Ti 4+ , Nb 5+ , W 6+ and Bi 3+ , Including Cation ratio of the total content of La 3+ , Gd 3+ , Y 3+ and Yb 3+ to the total content of Ti 4+ , Nb 5+ , W 6+ and Bi 3+ ((La 3+ + Gd 3+ + Y 3+ + Yb 3+ ) / (Ti 4+ + Nb 5+ + W 6+ + Bi 3+ )) is 1.90 to 7.00, and
- the refractive index nd is in the range of 1.88 to 2.00
- the Abbe number ⁇ d is in the range of 28.0 to 34.0
- the following formula: ⁇ Pg, F Pg, F + (0.0018 ⁇ ⁇ d)
- a further aspect of the present invention relates to a glass gob for press molding made of the above optical glass.
- a further aspect of the present invention relates to an optical element blank made of the above optical glass.
- a further aspect of the present invention relates to an optical element made of the above optical glass.
- an optical glass having high refractive index and low dispersion characteristics and suitable for correcting high-order chromatic aberration, and a glass gob for press molding made of the glass, an optical element blank, and an optical element. Can do.
- FIG. 1 is a digital camera photograph showing that an optical glass having a cation ratio (Y 3+ / (La 3+ + Gd 3+ + Y 3+ + Yb 3+ )) exceeding 0.180 is inferior in glass stability.
- FIG. 2 is a digital camera photograph showing that an optical glass having a cation ratio (Y 3+ / (La 3+ + Gd 3+ + Y 3+ + Yb 3+ )) exceeding 0.180 is inferior in glass stability.
- FIG. 3 is a plot of ⁇ Pg, F calculated from the above formula against the Abbe number ⁇ d for the optical glass shown in Table 1, the example of US2011 / 0028300A1, and the example of Japanese Patent Application Laid-Open No. 2010-30879. It is a graph.
- the total content of Si 4+ and B 3+ is in the range of 10-60 cation%
- the total content of La 3+ , Gd 3+ , Y 3+ and Yb 3+ ranges from 25 to 70 cation%
- the total content of Ti 4+ , Nb 5+ , W 6+ and Bi 3+ is in the range of 10-20 cation%
- Li + content is in the range of 0-5.0 cation%
- the Ge content is less than 5.0% by weight as GeO 2 in the oxide-based glass composition; Does not contain Pb
- the cation ratio of the Si 4+ content to the B 3+ content (Si 4+ / B 3+ ) is 0.70 or less, Cation ratio of the total content of La 3+ , Gd 3+ , Y 3+ and Yb 3+ to the total content of Ti 4+ , Nb 5+ , W 6+ and Bi 3+ ((La 3+ + Gd 3+ + Y 3+ + Yb
- Si 4+ and B 3+ are both components for forming a glass network and are effective components for maintaining glass stability. If the total content of Si 4+ and B 3+ is less than 10%, the glass stability deteriorates, the liquidus temperature rises, and if the total content exceeds 60%, it is difficult to achieve a desired refractive index. become. Therefore, the total content of Si 4+ and B 3+ is 10 to 60%. Specifically, it may be 10.0 to 60.0%.
- the upper limit of the total content of Si 4+ and B 3+ is preferably 50%, specifically 50.0%, more preferably 45%, specifically 45.0%, and still more preferably 43%, more specifically 43. 0%, more preferred upper limit is 42%, specifically 42.0%, even more preferred upper limit is 41%, specifically 41.0%.
- the preferred lower limit of the total content of Si 4+ and B 3+ is 15%. %, Specifically 15.0%, more preferable lower limit is 20%, specifically 20.0%, further preferable lower limit is 25%, specifically 25.0%, more preferable lower limit is 30%, specifically 30.0%. A more preferred lower limit is 35%, specifically 35.0%.
- the cation ratio of Si 4+ content to B 3+ content prevents the rise of liquid phase temperature and excessive rise of glass transition temperature and maintains meltability and devitrification resistance.
- 3+ is 0.70 or less. Preferably it is 0.65 or less, more preferably 0.6 or less, even more preferably 0.5 or less, even more preferably 0.45 or less, even more preferably 0.4 or less, and even more preferably 0.35 or less.
- the cation ratio (Si 4+ / B 3+ ) should be 0.05 or more from the viewpoints of improving the thermal stability of glass, achieving viscosity suitable for molding molten glass, and improving chemical durability. Preferably, it is 0.1 or more.
- La 3+ , Gd 3+ , Y 3+ , and Yb 3+ are components having a high refractive index and a low dispersion, improve chemical durability, lower ⁇ Pg, F, and also improve glass coloration. . If the total content of La 3+ , Gd 3+ , Y 3+ and Yb 3+ is less than 25%, the above effect cannot be obtained, and it becomes difficult to realize a desired refractive index and Abbe number. On the other hand, when the total content of La 3+ , Gd 3+ , Y 3+ and Yb 3+ exceeds 70%, the glass stability deteriorates and the liquidus temperature rises.
- the total content of La 3+ , Gd 3+ , Y 3+ and Yb 3+ is set to 25 to 70%. Specifically, the content may be 25.0-70.0%.
- the preferable upper limit of the total content of La 3+ , Gd 3+ , Y 3+ and Yb 3+ is 60%, specifically 60.0%, more preferably 55%, specifically 55.0%, and further preferable upper limit. Is 50%, specifically 50.0%, more preferably 45%, specifically 45.0%, more preferably 40%, more specifically 40.0%, and still more preferably 38%.
- the preferable lower limit of the total content of La 3+ , Gd 3+ , Y 3+ and Yb 3+ is 28%, specifically 28.0%, more preferably 30%, and more specifically 30%. 0.0%, more preferable lower limit is 31%, specifically 31.0%, even more preferable lower limit is 32%, specifically 32.0%, still more preferable lower limit is 33%, specifically 33.0%, particularly preferable.
- the lower limit is 34%, specifically 34.0% .
- Ti 4+ , Nb 5+ , W 6+ and Bi 3+ are high refractive index and high dispersion components that increase the refractive index and reduce the Abbe number. Moreover, these work to improve devitrification resistance, suppress an increase in liquidus temperature, and improve chemical durability. If the total content of Ti 4+ , Nb 5+ , W 6+ and Bi 3+ is less than 10%, it is difficult to obtain the above effect, but Ti 4+ , Nb 5+ , W 6+ and Bi 3+ If the total content exceeds 20%, the dispersion becomes too high, ⁇ Pg, F increases, and the glass becomes more colored. Therefore, the total content of Ti 4+ , Nb 5+ , W 6+ and Bi 3+ is 10 to 20%.
- the content may be 10.0 to 20.0%.
- the upper limit of the total content of Ti 4+ , Nb 5+ , W 6+ and Bi 3+ is preferably 19.5%, more preferably 19%, specifically 19.0%, and further preferably 18.5%.
- the more preferable upper limit is 18%, specifically 18.0%, and the still more preferable upper limit is 17.5%.
- the preferable lower limit of the total content of Ti 4+ , Nb 5+ , W 6+ and Bi 3+ is 11%, specifically 11.0%, more preferable lower limit is 12%, specifically 12.0%, more preferable lower limit is 13%, specifically 13.0%, more preferable lower limit is 13.5%, even more preferable.
- the lower limit is 14%, specifically 14.0%, and a still more preferable lower limit is 14.5%.
- the range of the cation ratio ((La 3+ + Gd 3+ + Y 3+ + Yb 3+ ) / (Ti 4+ + Nb 5+ + W 6+ + Bi 3+ )) is set to 1.90 to 7.00.
- the preferable upper limit of the cation ratio ((La 3+ + Gd 3+ + Y 3+ + Yb 3+ ) / (Ti 4+ + Nb 5+ + W 6+ + Bi 3+ )) is 6.00, more preferably 5.00,
- the preferable upper limit is 4.00, the more preferable upper limit is 3.50, the still more preferable upper limit is 3.00, the still more preferable upper limit is 2.85, the preferable lower limit of the cation ratio is 1.95, and the more preferable lower limit is 1.98, a more preferred lower limit is 2.00, a still more preferred lower limit is 2.03, a still more preferred lower limit is 2.05, and a still more preferred lower limit is 2.10.
- the cation ratio of the content (Y 3+ / (La 3+ + Gd 3+ + Y 3+ + Yb 3+ )) is 0.180 or less. From the above viewpoint, the cation ratio (Y 3+ / (La 3+ + Gd 3+ + Y 3+ + Yb 3+ )) is preferably 0.150 or less, more preferably 0.130 or less, and further preferably 0.100. It is as follows.
- the cation ratio (Y 3+ / (La 3+ + Gd 3+ + Y 3+ + Yb 3+ )) can be set to 0, By containing a small amount of Y 3+ , the liquidus temperature can be lowered and the devitrification resistance can be improved, so that the cation ratio (Y 3+ / (La 3+ + Gd 3+ + Y 3+ + Yb 3+ )) Is preferably 0.020 or more.
- optical glass having a refractive index nd of more than 1.920 it is effective to use optical glass having a refractive index nd of more than 1.920 in order to increase the functionality and compactness of a glass optical element and an optical system incorporating the optical element.
- the refractive index nd exceeds 2.000, the glass stability tends to be lowered, so that an optical element material effective for increasing the functionality and compactness of the optical system is provided while maintaining the stability of the glass. Therefore, the range of the refractive index nd is set to be over 1.920 and not more than 2.000.
- the preferable upper limit of the refractive index nd is 1.980, the more preferable upper limit is 1.970, the further preferable upper limit is 1.960, the more preferable upper limit is 1.955, and the preferable lower limit of the refractive index nd is 1.925, more preferable.
- the lower limit is 1.930, the more preferable lower limit is 1.940, and the more preferable lower limit is 1.945.
- the lower limit of the refractive index may be preferably 1.88 or more, 1.90 or more, or 1.92 or more.
- the lower limit of the Abbe number ⁇ d is set to 28.0 to provide an optical element material suitable for chromatic aberration correction by taking advantage of the low dispersibility, thereby maintaining and improving the glass stability. Therefore, the upper limit of Abbe number ⁇ d is set to 34.0. That is, the Abbe number ⁇ d ranges from 28.0 to 34.0. A preferable upper limit of the Abbe number ⁇ d is 33.5, and a more preferable upper limit is 33.0. A preferable lower limit of the Abbe number ⁇ d is 29.0, a more preferable lower limit is 30.0, a still more preferable lower limit is 30.5, and a more preferable value. The lower limit is 31.0, the more preferred lower limit is 31.5, and the still more preferred lower limit is 32.0.
- the yield point is over 645 ° C.
- the cold workability of glass is indirectly related to the yield point.
- a glass with a low yield point is more suitable for precision press molding than cold workability, whereas a glass with a high yield point is more suitable for cold work than precision press molding and is excellent in cold workability. Therefore, in the optical glass according to one embodiment of the present invention, the yield point is not excessively lowered and is higher than 645 ° C.
- the yield point is preferably 660 ° C. or higher, more preferably 680 ° C. or higher, further preferably 700 ° C. or higher, more preferably 720 ° C. or higher, and even more preferably 740 ° C. or higher.
- the yielding point is preferably 850 ° C. or lower.
- the optical glass according to one embodiment of the present invention has a small ⁇ Pg, F while the refractive index nd is more than 1.920 and not more than 2.000, and the Abbe number ⁇ d is in the range of 30.0 to 34.0.
- Such an optical glass is suitable as an optical element material for correcting higher-order chromatic aberration.
- the partial dispersion ratios Pg and F are expressed as (ng ⁇ nF) / (nF ⁇ nC) using the refractive indexes ng, nF and nC in the g-line, F-line and c-line.
- ng, nF, and nC are values determined by the method shown in the examples described later.
- ⁇ Pg, F is set to 0.0005 or less in order to provide an optical glass suitable for high-order chromatic aberration correction.
- a preferable range of ⁇ Pg, F is 0.0004 or less, a more preferable range is 0.0003 or less, and a further preferable range is 0.0002 or less.
- the more preferable range is 0.0001 or less, and the still more preferable range is 0.0000 or less.
- the cation ratio of Ti 4+ content relative Nb 5+ content is 4.00
- the cation ratio (Ti 4+ / Nb 5+ ) is preferably 3.50 or less, more preferably 3.00 or less, and 2.50 or less. More preferably, it is more preferably 2.00 or less.
- the cation ratio (Ti 4+ / Nb 5+ ) is preferably 0.05 or more and more preferably 0.1 or more from the viewpoint of improving devitrification resistance and suppressing an increase in liquidus temperature. , More preferably 0.15 or more, and still more preferably 0.2 or more.
- ⁇ Pg, F tends to increase as the Abbe number ⁇ d decreases.
- a high refractive index glass having a small ⁇ Pg, F is desired.
- a preferred specific embodiment of the composition adjustment for setting ⁇ Pg, F to 0.0005 or less in an Abbe number ⁇ d of 34.0 or less is as follows: Cation ratio of the total content of La 3+ , Gd 3+ , Y 3+ and Yb 3+ to the total content of Si 4+ and B 3+ [(La 3+ + Gd 3+ + Y 3+ + Yb 3+ ) / (Si 4+ + B 3+ )] is 0.83 or more, Cation ratio of the total content of Ti 4+ , Nb 5+ , W 6+ and Bi 3+ to the total content of Si 4+ and B 3+ [(Ti 4+ + Nb 5+ + W 6+ + Bi 3+ ) / (Si 4+ + B 3+ )] is set to 0.31 or more, Satisfying at least one of the above, or satisfying both.
- the more preferable lower limit of the cation ratio [(La 3+ + Gd 3+ + Y 3+ + Yb 3+ ) / (Si 4+ + B 3+ )] is 0.84, the more preferable lower limit is 0.85, and the more preferable lower limit is 0.8. 86.
- the more preferable lower limit of the cation ratio [(Ti 4+ + Nb 5+ + W 6+ + Bi 3+ )] / (Si 4+ + B 3+ )] is 0.34, the more preferable lower limit is 0.35, and the more preferable lower limit is 0.00. 36, a much more preferred lower limit is 0.37, a still more preferred lower limit is 0.38, and a still more preferred lower limit is 0.39.
- the upper limit of the cation ratio [(La 3+ + Gd 3+ + Y 3+ + Yb 3+ ) / (Si 4+ + B 3+ )] is naturally determined from the glass composition that the optical glass according to one embodiment of the present invention should have, For example, it can be 2.0 or less.
- the preferred upper limit of the cation ratio [(La 3+ + Gd 3+ + Y 3+ + Yb 3+ ) / (Si 4+ + B 3+ )] is 1.6, more preferred upper limit. 1.4, a more preferred upper limit is 1.2, a more preferred upper limit is 1.0, and a still more preferred upper limit is 0.98.
- the upper limit of the cation ratio [(Ti 4+ + Nb 5+ + W 6+ + Bi 3+ ) / (Si 4+ + B 3+ )] is naturally determined from the glass composition that the optical glass according to one embodiment of the present invention should have. However, it can be, for example, 1.5 or less. It can be. From the standpoint of maintaining the thermal stability of the glass, the preferred upper limit of the cation ratio [(Ti 4+ + Nb 5+ + W 6+ + Bi 3+ ) / (Si 4+ + B 3+ )] is 1.2, more preferred upper limit. 1.0, a more preferred upper limit is 0.8, a still more preferred upper limit is 0.7, a still more preferred upper limit is 0.6, and a still more preferred upper limit is 0.5.
- Li + is particularly strong in reducing the glass transition temperature among alkali metal components. Therefore, if the Li + content is too high, the glass transition temperature is lowered, and the workability during grinding and polishing is lowered. Therefore, the Li + content is preferably determined so that the glass transition temperature does not decrease. From the above viewpoint, the Li + content is in the range of 0 to 5.0%. A preferable range of the Li + content will be described later.
- Ge is a component that forms a glass network, and also functions to increase the refractive index. Therefore, Ge is a component that can increase the refractive index while maintaining glass stability, but it is a component that is significantly more expensive than other components. It is a component that is desired to refrain from its content. In the optical glass according to one aspect of the present invention, desired optical characteristics can be obtained even if the Ge content is suppressed to less than 5.0% by mass as the GeO 2 amount in the oxide-based glass composition by the composition adjustment described above and below. And the realization of excellent glass stability.
- the amount of GeO 2 is preferably 0 to 4% by mass, specifically 0 to 4.0% by mass, more preferably 0 to 3% by mass, specifically 0 to 3.0% by mass, and further preferably 0 to 2% by mass. Specifically, it is in the range of 0 to 2.0% by mass, more preferably 0 to 1% by mass, specifically 0 to 1.0% by mass, and still more preferably 0% by mass, that is, Ge-free glass. Particularly preferred.
- the “oxide-based glass composition” refers to a glass composition obtained by converting all glass raw materials to be decomposed when melted and existing as oxides in the optical glass.
- Si 4+ is a glass network forming component as described above, and is an effective component for maintaining glass stability, maintaining viscosity suitable for molding molten glass, and improving chemical durability.
- the content of Si 4+ is preferably 1% or more, more preferably 3% or more, more preferably 3.0% or more, and more preferably 4% or more, specifically 4.0%. More preferably, it is more preferably 5% or more, more preferably 5.0% or more, more preferably 6% or more, and more preferably 6.0% or more, and more preferably 7% or more. Is more preferably 7.0% or more, more preferably 8% or more, and still more preferably 8.0% or more.
- the desired refractive index realizes an Abbe number, and suppress an increase in liquidus temperature and glass transition temperature, devitrification resistance, from maintaining the meltability than 30% the content of Si 4+, Specifically, it is preferably 30.0% or less, more preferably 25% or less, more preferably 25.0% or less, further preferably 20% or less, and more preferably 20.0% or less. % Or less, specifically 18.0% or less, more preferably 15% or less, more preferably 15.0% or less, even more preferably 12% or less, specifically 12.0% or less. Is more preferably 11% or less, and more preferably 11.0% or less.
- B 3+ is a glass network forming component as described above, and is an essential component effective for maintaining the meltability of the glass, lowering the liquidus temperature, improving the glass stability, and reducing the dispersion.
- the content of B 3+ is preferably 5% or more, more preferably 10% or more, more preferably 10.0% or more, and more preferably 15% or more, specifically 15.0. % Or more, more preferably 20% or more, more preferably 20.0% or more, more preferably 25% or more, more preferably 25.0% or more, more preferably 28% or more, It is still more preferable to make it 28.0% or more.
- the B 3+ content is preferably 55% or less, more preferably 55.0% or less, and more preferably 45% or less. More preferably, it should be 45.0% or less, more preferably 40% or less, more preferably 40.0% or less, still more preferably 38% or less, more preferably 38.0% or less, and even more preferably 35% In the following, it is more preferably 35.0% or less, more preferably 33% or less, and more preferably 33.0% or less.
- La 3+ is a component excellent in the function of reducing the high refractive index and low dispersion while maintaining the glass stability. It also serves to reduce ⁇ Pg, F.
- the La 3+ content is preferably 10% or more, specifically 10.0% or more, more preferably 15% or more, and more preferably 15.0% or more. % Or more, more preferably 18.0% or more, more preferably 20% or more, more preferably 20.0% or more, more preferably 22% or more, and more preferably 22.0% or more. More preferably, it is more preferably 24% or more, more preferably 24.0% or more, even more preferably 26% or more, and more preferably 26.0% or more.
- the La 3+ content is preferably 50% or less, specifically 50.0% or less, and preferably 45% or less. Is more preferably 45.0% or less, more preferably 40% or less, more preferably 40.0% or less, even more preferably 35% or less, and more preferably 35.0% or less. % Or less, more preferably 33.0% or less, even more preferably 32% or less, specifically 32.0% or less, even more preferably 31% or less, specifically 31.0% or less. Even more preferred.
- Gd 3+ , Y 3+ , and Yb 3+ all work together with La 3+ to lower the liquidus temperature and greatly improve devitrification resistance. It also serves to reduce ⁇ Pg, F.
- the total content of Gd 3+ , Y 3+ and Yb 3+ is preferably 0.5% or more, more preferably 1% or more, more specifically 1.0% or more. Preferably, it is more preferably 2% or more, specifically 2.0% or more, more preferably 3% or more, more preferably 3.0% or more, still more preferably 4% or more. % Or more, more preferably 5.5% or more.
- the total content of Gd 3+ , Y 3+ and Yb 3+ is 35% or less, specifically 35.0% or less. 30% or less, more preferably 30.0% or less, more preferably 25% or less, more preferably 25.0% or less, further preferably 20% or less, specifically 20.0%. More preferably, it is more preferably 15% or less, more preferably 15.0% or less, even more preferably 10% or less, and even more preferably 10.0% or less, even more preferably 7% or less. In detail, it is still more preferable to set it as 7.0% or less.
- the preferred range of the content of Gd 3+ is 0 to 20%. Specifically, it can be in the range of 0 to 20.0%.
- the upper limit of the content of Gd 3+ is preferably 15%, specifically 15.0%, more preferably 13%, specifically 13.0%, more preferably 11%, specifically 11.0%, and more preferably.
- the upper limit is 9%, specifically 9.0%, and a more preferable upper limit is 7%, specifically 7.0%.
- a preferred lower limit of the content of Gd 3+ is 0.5%, a more preferred lower limit is 1%, specifically 1.0%, a further preferred lower limit is 2%, specifically 2.0%, a more preferred lower limit is 3%, Specifically, the lower limit is 3.0%, and a more preferable lower limit is 4%, specifically 4.0%. Note that the content of Gd 3+ may be 0%.
- the preferred range of the Y 3+ content is 0 to 15%, specifically 0 to 15.0%.
- the preferable upper limit of the content of Y 3+ is 10%, specifically 10.0%, more preferably 7%, specifically 7.0%, more preferably 5%, specifically 5.0%, and more preferably.
- the upper limit is 3%, specifically 3.0%, and a more preferable upper limit is 2%, specifically 2.0%.
- the minimum with preferable content of Y ⁇ 3+ > is 0.1%. Note that the content of Y 3+ may be 0%.
- the preferred range of the content of Yb 3+ is 0 to 10%, specifically 0 to 10.0%, more preferably 0 to 6%, Specifically, 0 to 6.0%, more preferably 0 to 4%, specifically 0 to 4.0%, and still more preferably 0 to 2%, and more specifically 0 to 2.0%.
- the content of Yb 3+ can also be set to 0%. Since Yb 3+ has absorption in the infrared region, it is not suitable for use in high-sensitivity optical systems that require photosensitive characteristics in the near-infrared region, such as high-precision video cameras and surveillance cameras. Glass with a reduced content of Yb 3+ is suitable for the above applications.
- the amount of Yb 2 O 3 in the oxide-based glass composition is preferably less than 2% by mass, more preferably 1.8% by mass or less, and even more preferably 1.5% by mass or less.
- 1.2 mass% or less more preferably 1.0 mass% or less, 0.9 mass% or less, 0.8 mass% or less, 0.7 mass% or less, 0.6 mass% or less, It is preferable in the order of 0.5 mass% or less, 0.3 mass% or less, 0.1 mass% or less, and 0 mass%.
- Ti 4+ , Nb 5+ , W 6+ , and Bi 3+ increase the refractive index and decrease the Abbe number as described above, improve devitrification resistance, suppress the increase in liquidus temperature, It works to improve physical durability.
- Ta 5+ is a component that can perform the same function.
- the total content of Ti 4+ , Nb 5+ , Ta 5+ , W 6+ and Bi 3+ is 13% or more, specifically 13.0% or more. It is more preferably 5% or more, more preferably 14% or more, more preferably 14.0% or more, still more preferably 14.5% or more.
- Ti 4+ , Nb 5+ , Ta 5+ , W 6+ and Bi 3+ total content is preferably 30% or less, specifically 30.0% or less, more preferably 28% or less, and more preferably 28.0% or less, more preferably 26%
- it is more preferably 26.0% or less in detail, more preferably 24% or less, more preferably 24.0% or less, more preferably 22% or less, and more preferably 22.0% or less. More preferably, it is 20% or less, more specifically 20.0% or less, still more preferably 17.5% or less.
- Ti 4+ has the effect of increasing ⁇ Pg, F in addition to the above effects. Therefore, the preferable upper limit of the content of Ti 4+ is 18%, specifically 18.0%, more preferable upper limit is 17%, specifically 17.0%, further preferable upper limit is 16%, specifically 16.0%, A more preferred upper limit is 15%, specifically 15.0%, a still more preferred upper limit is 14%, specifically 14.0%, a still more preferred upper limit is 13%, specifically 13.0%, and a still more preferred upper limit is 12. %, Specifically 12.0%. Ti 4+ improves devitrification resistance among the components having a high refractive index and high dispersion, and is excellent in the effect of suppressing the rise in liquidus temperature.
- the preferable lower limit of the content of Ti 4+ is 1%, specifically 1.0%, more preferably the lower limit is 2%, specifically 2.0%, more preferably the lower limit is 3%, specifically 3.0%, A more preferred lower limit is 4%, specifically 4.0%, a still more preferred lower limit is 5%, specifically 5.0%, a still more preferred lower limit is 6%, specifically 6.0%, and a still more preferred lower limit is 7%. %, Specifically 7.0%.
- Nb 5+ has the effect of increasing ⁇ Pg, F in addition to the above effects, but is a component that hardly increases ⁇ Pg, F compared to Ti 4+ and W 6+ . Therefore, the preferable upper limit of the Nb 5+ content is 30%, specifically 30.0%, more preferably 25%, specifically 25.0%, more preferably 20%, specifically 20.0%, A more preferable upper limit is 15%, specifically 15.0%, a still more preferable upper limit is 10%, specifically 10.0%, and an even more preferable upper limit is 8%, specifically 8.0%. Nb 5+ improves devitrification resistance among the components with high refractive index and high dispersion, and is excellent in the effect of suppressing the rise in liquidus temperature.
- the preferable lower limit of the Nb 5+ content is 0.5%
- the more preferable lower limit is 1%, specifically 1.0%
- the more preferable lower limit is 2%
- the specific limit is 2.0%
- the more preferable lower limit is 3. %, Specifically 3.0%, a more preferred lower limit is 4%, specifically 4.0%, and a still more preferred lower limit is 5%, specifically 5.0%.
- Ta 5+ has the effect of increasing ⁇ Pg, F in addition to the above effects, but is a component that hardly increases ⁇ Pg, F compared to Ti 4+ , W 6+ , and Nb 5+ . Therefore, the preferable range of the content of Ta 5+ is 0 to 10%, specifically 0 to 10.0%, more preferably 0 to 8%, specifically 0 to 8.0%, and still more preferably 0 to 10%. 6%, specifically 0-6.0%, more preferable range is 0-4%, specifically 0-4.0%, even more preferable range is 0-2%, specifically 0-2.0%. .
- the Ta 5+ content can also be set to 0%.
- Ta 5+ is a component that is difficult to increase ⁇ Pg, F compared with Ti 4+ , Nb 5+ , W 6+ , and Bi 3+ , but is a rare material and has a high raw material cost. Therefore, it is preferable to reduce the content of Ta 5+ from the viewpoint of stably providing the optical glass.
- Ti 4+, Nb 5+, W 6+, the content of the cation ratio of Ta 5+ to the total content of Bi 3+ and Ta 5+ (Ta 5+ / (Ti 4+ + Nb 5+ + W 6+ + Bi 3+ + Ta 5+ )) is preferably 0.45 or less, more preferably 0.40 or less, further preferably 0.30 or less, and 0.20 or less. Is more preferable, and it is still more preferable to set it to 0.10 or less, and it is especially preferable that it is 0.00.
- the preferable range of the content of W 6+ is 0 to 10%, specifically 0 to 10.0S%, more preferably 0 to 7%, specifically 0 to 7.0%, and still more preferably 0 to 10%. 5%, specifically 0-5.0%, more preferable range is 0-3%, specifically 0-3.0%, even more preferable range is 0-2%, specifically 0-2.0%. .
- the content of W 6+ can be made 0%.
- the amount of WO 3 in the oxide-based glass composition is preferably less than 10% by mass, more preferably less than 9% by mass, further preferably 8% by mass or less, and 7% by mass. More preferably, it may be 0 mass%.
- Bi 3+ has the effect of increasing ⁇ Pg, F in addition to the above effects.
- the glass raw material for introducing Bi 3+ may contain a large amount of rare earth components, and glass having a high melting temperature may increase the coloration of the glass. Therefore, the preferable range of the Bi 3+ content is 0 to 10%, specifically 0 to 10.0%, more preferably 0 to 6%, specifically 0 to 6.0%, and still more preferably 0 to 10%. 4%, specifically 0-4.0%, more preferable range is 0-2%, specifically 0-2.0%, even more preferable range is 0-1%, specifically 0-1.0%. .
- the Bi 3+ content can also be reduced to 0%.
- Zr 4+ functions to increase the refractive index and improve chemical durability, to improve devitrification resistance by coexisting with Ti 4+, and to suppress increase in liquidus temperature.
- the preferable upper limit of the content of Zr 4+ is 15%, specifically 15.0%.
- the preferable upper limit of the content of Zr 4+ is 10%, specifically 10.0%, more preferably the upper limit is 8%, specifically 8.0%, the more preferable upper limit is 7%, specifically 7.0%.
- a more preferable lower limit of the content of Zr 4+ is 2%, specifically 2.0%, a further preferable lower limit is 3%, specifically 3.0%, and a more preferable lower limit is 4%, specifically 4.0%. .
- the preferred range of the Zn 2+ content is 0 to 15%, specifically 0 to 15.0%.
- the content of Zn 2+ is more preferably 12% or less, specifically 12.0% or less, further preferably 10% or less, specifically 10.0% or less, more preferably 8% or less, and more specifically 8.0. % Or less, more preferably 6% or less, specifically 6.0% or less, even more preferably less than 6.0%, still more preferably 5.5% or less, and still more preferably 5% or less. Is 5.0% or less, particularly preferably 4.5% or less.
- Zn 2+ which has an effect of improving meltability and clarity.
- the preferred lower limit of the Zn 2+ content is 0.1%, the more preferred lower limit is 0.5%, the still more preferred lower limit is 0.8%, the more preferred lower limit is 1%, specifically 1.0%, even more preferred.
- the lower limit is 1.5%, and an even more preferable lower limit is 2%, specifically 2.0%.
- the total content of La 3+ , Gd 3+ , Y 3+ , Yb 3+ , Ti 4+ , Nb 5+ , Zr 4+ , Ta 5+ , W 6+ Is preferably 50% or more, more preferably 51% or more, still more preferably 52% or more, still more preferably 53% or more, and even more preferably 54% or more. And more preferably 55% or more.
- Li + , Na + and K + are optional components that serve to improve the meltability and lower the glass transition temperature.
- the total content of Li + , Na + and K + is in the range of 0 to 10%. Specifically, it is preferably in the range of 0 to 10.0%.
- a more preferable range of the total content of Li + , Na + and K + is 0 to 8%, specifically 0 to 8.0%, more preferable range is 0 to 6%, specifically 0 to 6.0%, A preferred range is 0 to 4%, specifically 0 to 4.0%, a still more preferred range is 0 to 2%, specifically 0 to 2.0%, an even more preferred range is 0 to 1%, specifically 0 to It is particularly more preferable that it is 1.0% and does not contain the alkali metal component.
- a preferable range is 0 to 10%, specifically 0 to 10.0%, more preferably 0 to 7%, and more specifically 0 to 7. 0%, more preferred range is 0-5%, specifically 0-5.0%, more preferred range is 0-4%, more specifically 0-4.0%, more preferred range is 0-3%, more specifically 0 to 3.0%, a more preferable range is 0 to 2%, specifically 0 to 2.0%, an even more preferable range is 0 to 1%, specifically 0 to 1.0%. Even more preferably, no alkali metal component is included.
- Mg 2+ , Ca 2+ , Sr 2+ and Ba 2+ work to improve the meltability of the glass and lower the glass transition temperature Tg. Moreover, the defoaming effect can also be obtained by introducing it into glass in the form of nitrate or sulfate. As the total content of Mg 2+ , Ca 2+ , Sr 2+ and Ba 2+ increases, the liquidus temperature tends to increase, and devitrification resistance, refractive index and chemical durability tend to decrease. Indicates. The total content of Mg 2+ , Ca 2+ , Sr 2+ and Ba 2+ is set to 0 to 10 in order to suppress the rise in liquidus temperature and maintain devitrification resistance, refractive index and chemical durability.
- a more preferable range of the total content of Mg 2+ , Ca 2+ , Sr 2+ and Ba 2+ is 0 to 8%, specifically 0 to 8.0%, more preferably 0 to 6%, and more specifically 0. -6.0%, more preferable range is 0-4%, specifically 0-4.0%, even more preferable range is 0-2%, specifically 0-2.0%, still more preferable range is 0- 1%, specifically 0 to 1.0%, and does not need to contain the alkaline earth metal component.
- the preferred range is 0 to 10%, specifically 0 to 10.0%, and the more preferred range is 0 to 7%. Specifically, 0 to 7.0%, more preferably 0 to 5%, specifically 0 to 5.0%, more preferably 0 to 3%, more preferably 0 to 3.0%, and still more preferably The range is 0 to 2%, specifically 0 to 2.0%, more preferably 0 to 1%, and more specifically 0 to 1.0%.
- the above alkaline earth metal components may not be contained.
- Ge 4+ is a component that forms a glass network and also works to increase the refractive index. Therefore, Ge 4+ is a component that can increase the refractive index while maintaining glass stability, but it is significantly more expensive than other components. It is a component that is desired to refrain from its content.
- the Ge 4+ content is preferably 0 to 10%, more specifically 0 to 10.0%.
- a more preferable range of the content of Ge 4+ is 0 to 8%, specifically 0 to 8.0%, a further preferable range is 0 to 6%, specifically 0 to 6.0%, and a more preferable range is 0 to 4%. %, Specifically 0-4.0%, further 0-3.5%, 0-3%, more specifically 0-3.0%, 0-2.5%, 0-2%, more specifically 0- 2.0%, 0 to 1.5%, and 0 to 0.5 are more preferable in this order. It is particularly preferable not to contain Ge 4+ , that is, a Ge-free glass.
- the content of Al 3+ is preferably 0 to 10%, more specifically 0 to 10.0%.
- a more preferable range of the content of Al 3+ is 0 to 8%, specifically 0 to 8.0%, a further preferable range is 0 to 6%, specifically 0 to 6.0%, and a more preferable range is 0 to 4%.
- % Specifically 0 to 4.0%, a more preferable range is 0 to 2%, specifically 0 to 2.0%, an even more preferable range is 0 to 1%, specifically 0 to 1.0%. It is particularly preferred not to contain Al 3+ .
- Te 4+ works to increase the refractive index, but considering the environmental load, its content is preferably 0 to 10%, more specifically 0 to 10.0%.
- a more preferable range of the Te 4+ content is 0 to 8%, specifically 0 to 8.0%, a further preferable range is 0 to 6%, specifically 0 to 6.0%, and a more preferable range is 0 to 4%.
- % Specifically 0 to 4.0%, a more preferable range is 0 to 2%, specifically 0 to 2.0%, an even more preferable range is 0 to 1%, specifically 0 to 1.0%. Even more preferably less than 0.5%, even more preferably less than 0.3%, still more preferably less than 0.1% and does not contain Te 4+ , That is, Te-free glass is particularly preferable.
- the content of any cation component other than the above cation component is preferably 0 to 5%, more preferably 0 to 4%, more specifically 0 to 4.0%. Is more preferably 0 to 3%, more preferably 0 to 3.0%, still more preferably 0 to 2.5%, more preferably 0 to 2%, and more specifically 0 to 2.0%. Is more preferably 0 to 1.5%, still more preferably 0 to 1%, more preferably 0 to 1.0%, still more preferably 0 to 0.5%. It is particularly preferable to do this.
- the content of any cation component other than the cation component may be 0%.
- the optical glass according to one embodiment of the present invention does not need to contain components such as Lu, Hf, Ga, In, and Sc because glass stability can be maintained while achieving required optical characteristics. Since Lu, Hf, Ga, In and Sc are also expensive components, it is preferable to suppress the contents of Lu 3+ , Hf 4+ , Ga 3+ , In 3+ and Sc 3+ to 0 to 1.0%, respectively. It is more preferable to suppress each to 0 to 0.5%. Lu 3+ is not introduced, Hf 4+ is not introduced, Ga 3+ is not introduced, In 3+ is not introduced, Sc 3+ It is particularly preferred that each be not introduced.
- Sb can be added as a refining agent, and even when added in a small amount, it also serves to suppress a decrease in light transmittance due to the inclusion of impurities such as Fe.
- impurities such as Fe.
- the amount of Sb added in terms of Sb 2 O 3 is preferably 0 to 1% by mass, more preferably 0 to 0.5% by mass, and still more preferably 0 to 0.1% by mass. .
- Sn can also be added as a refining agent. However, if it is added in excess of 1% by mass in terms of SnO 2 , the glass is colored, or the molding surface deterioration of the mold is promoted by oxidation. Accordingly, the addition amount of Sn in terms of SnO 2 is preferably 0 to 1% by mass, more preferably 0 to 0.5% by mass on an external basis.
- Ce oxides, sulfates, nitrates, chlorides, and fluorides can be added in small amounts as clarifying agents. In consideration of environmental impact, it is preferable not to introduce As, Pb, U, Th, or Cd.
- the optical glass according to one embodiment of the present invention does not contain Pb. Furthermore, it is preferable not to introduce a substance that causes coloring such as Cu, Cr, V, Fe, Ni, Co, Nd, and Tb from the viewpoint of taking advantage of the excellent light transmittance of glass.
- a substance that causes coloring such as Cu, Cr, V, Fe, Ni, Co, Nd, and Tb from the viewpoint of taking advantage of the excellent light transmittance of glass.
- “not introduced”, “not contained”, and “content of component is 0%” means that this component is not introduced as a glass component. However, unintentional contamination as impurities is allowed.
- the optical glass according to one embodiment of the present invention is an oxide glass, and the main anion component is O 2 ⁇ .
- the main anion component is O 2 ⁇ .
- Cl ⁇ or F ⁇ as a fining agent.
- O 2 - preferably to 98 anionic% or more the content of, more preferably, to more than 99 anionic%, more preferably be at least 99.5 anionic%, it is more preferable to 100 anionic%.
- High refractive index glass has a large amount of high refractive index component (for example, La 3+ (La 2 O 3 ), Gd 3+ (Gd 2 O 3 ), Y 3+ (Y 2 O 3 ), Yb 3+ (Yb 2 O 3 ), Ti 4+ (TiO 2 ), Nb 5+ (Nb 2 O 5 ), Ta 5+ (Ta 2 O 5 ), W 6+ (WO 6 ), Zr 4+ (ZrO 2 )) Although contained, all of these components have an extremely high melting point.
- high refractive index component for example, La 3+ (La 2 O 3 ), Gd 3+ (Gd 2 O 3 ), Y 3+ (Y 2 O 3 ), Yb 3+ (Yb 2 O 3 ), Ti 4+ (TiO 2 ), Nb 5+ (Nb 2 O 5 ), Ta 5+ (Ta 2 O 5 ), W 6+ (WO 6 ), Zr 4+ (ZrO 2 )
- the melting temperature must be increased. As the melting temperature rises, the erodibility of the glass melt increases, and the melting vessel is eroded, and the materials that make up the vessel, such as platinum and platinum alloys, dissolve in the glass melt and color the glass or become platinum foreign matter. To do.
- the melting temperature is high, easily volatile components such as B 3+ volatilize, the glass composition changes with time, and the optical characteristics fluctuate.
- the melting temperature range may be considered as a temperature range in which a homogeneous glass melt can be obtained, and the lower limit of the temperature range may be considered to change generally in conjunction with the rise and fall of the liquidus temperature. Therefore, if the rise of the liquidus temperature can be suppressed, the rise of the melting temperature can also be suppressed. In addition, if the rise in liquidus temperature can be suppressed, it is effective for preventing devitrification during glass molding, and the viscosity of the glass can be adjusted to a range suitable for molding, making it easy to produce a high-quality glass molded body. Become.
- a preferred embodiment of the optical glass according to one embodiment of the present invention is a glass having a liquidus temperature of 1400 ° C. or lower.
- the preferable upper limit of the liquidus temperature is 1350 ° C.
- the more preferable upper limit is 1300 ° C.
- the still more preferable upper limit is 1280 ° C.
- the still more preferable upper limit is 1270 ° C.
- the still more preferable upper limit is 1260 ° C.
- the still more preferable upper limit is 1200 ° C.
- a lower limit of the liquidus temperature may be provided within a range where stable glass production is possible.
- the preferable lower limit of the liquidus temperature is 1100 ° C.
- the more preferable lower limit is 1150 ° C.
- the still more preferable lower limit is 1160 ° C.
- the still more preferable lower limit is 1170 ° C.
- the still more preferable lower limit is 1180 ° C.
- the optical glass according to one embodiment of the present invention is a high refractive index glass, generally, the specific gravity tends to increase when the glass has a high refractive index. However, an increase in specific gravity is not preferable because it causes an increase in the weight of the optical element.
- the optical glass according to one embodiment of the present invention can have a specific gravity of 6.00 or less even though it is a high refractive index glass by having the above glass composition. However, if the specific gravity is excessively reduced, the stability of the glass is lowered and the liquidus temperature tends to increase. Therefore, the specific gravity is preferably 4.00 or more.
- the more preferable upper limit of the specific gravity is 5.50, the more preferable upper limit is 5.30, the still more preferable upper limit is 5.20, and the still more preferable upper limit is 5.15.
- the more preferable lower limit of the specific gravity is 4.30, the more preferable lower limit is 4.50, the still more preferable lower limit is 4.80, and the still more preferable lower limit is 4.90.
- the optical glass according to one embodiment of the present invention can exhibit high light transmittance over a wide wavelength range in the visible range.
- ⁇ 70 exhibits a coloring degree of 500 nm or less.
- a more preferable range of ⁇ 70 is 480 nm or less, a further preferable range is 460 nm or less, a more preferable range is 440 nm or less, and a still more preferable range is 430 nm or less.
- the lower limit of ⁇ 70 is not particularly limited, but if the amount of the high refractive index and high dispersion component is excessively decreased to reduce ⁇ 70, the refractive index, Abbe number, and devitrification resistance can be maintained. Since it becomes difficult, it is preferable not to reduce ⁇ 70 excessively.
- the preferable lower limit of ⁇ 70 is 360 nm, the more preferable lower limit is 370 nm, the still more preferable lower limit is 380 nm, the more preferable lower limit is 390 nm, and the still more preferable lower limit is 400 nm.
- ⁇ 70 is a wavelength at which the light transmittance is 70% in the wavelength range of 280 to 700 nm.
- the light transmittance means that a glass sample having parallel surfaces polished to a thickness of 10.0 ⁇ 0.1 mm is used, and light is incident on the polished surface from a vertical direction.
- the obtained spectral transmittance that is, Iout / Iin where Iin is the intensity of light incident on the sample and Iout is the intensity of light transmitted through the sample.
- the spectral transmittance includes light reflection loss on the sample surface.
- polishing means that the surface roughness is smooth
- ⁇ 5 is a wavelength at which the light transmittance measured by the above-described method for ⁇ 70 is 5%.
- a preferable range of ⁇ 5 is 400 nm or less, a more preferable range is 390 nm or less, a more preferable range is 380 nm or less, and a more preferable range is It is 370 nm or less, and a still more preferable range is 360 nm or less.
- the preferable lower limit of ⁇ 5 is 300 nm, the preferable lower limit is 320 nm, the preferable lower limit is 330 nm, the preferable lower limit is 340 nm, and the preferable lower limit is 350 nm.
- the spectral transmittance is measured in the wavelength range of 280 to 700 nm.
- the light transmittance increases as the wavelength is increased from ⁇ 5, and when it reaches ⁇ 70, it reaches 70% or more up to the wavelength of 700 nm. Keep the high transmittance.
- the optical glass according to one embodiment of the present invention is a glass suitable for forming a smooth optical functional surface by polishing.
- the suitability of cold working such as polishing, that is, cold workability is indirectly related to the glass transition temperature.
- a glass with a low glass transition temperature is more suitable for precision press molding than cold workability, whereas a glass with a high glass transition temperature is more suitable for cold work than precision press molding. Excellent. Therefore, in the optical glass according to one embodiment of the present invention, it is preferable that the glass transition temperature is not excessively lowered, preferably over 630 ° C., more preferably 640 ° C. or higher, and 650 ° C. or higher. Is more preferably 660 ° C.
- the glass transition temperature is preferably 850 ° C. or lower, more preferably 800 ° C. or lower, and further preferably 750 ° C. or lower.
- the optical glass according to one aspect of the present invention is prepared by preparing a glass raw material so that the optical glass according to one aspect of the present invention is obtained, melting the glass raw material by heating, and molding the obtained molten glass.
- Can be manufactured For example, a powdery compound raw material or cullet raw material is weighed and prepared according to the target glass composition, supplied into a platinum or platinum alloy melting vessel, and then melted by heating. After the raw material is sufficiently melted and vitrified, the temperature of the molten glass is raised to clarify. The clarified molten glass is homogenized by stirring with a stirrer, and continuously supplied to and discharged from a glass outlet pipe, rapidly cooled and solidified to obtain a glass molded body. It is desirable that the melting temperature of the optical glass be in the range of 1250 to 1500 ° C. in order to obtain a glass that is homogeneous, low-colored, and stable in various properties including optical properties.
- ⁇ d represents the Abbe number.
- An optical glass having a deviation ⁇ Pg, F from the normal line of the partial dispersion ratios Pg, F calculated by: Is also provided.
- the description regarding the optical glass according to one embodiment of the present invention can be referred to.
- the glass gob for press molding according to one aspect of the present invention is made of the optical glass according to one aspect of the present invention.
- the shape of the gob is preferably a shape that facilitates press molding according to the shape of the target press-formed product. Moreover, it is preferable to set the mass of the gob according to the press-formed product.
- glass having excellent stability can be used, even if it is reheated, softened and press-molded, the glass is not easily devitrified, and a high-quality molded product can be stably produced. it can.
- the production example of the glass gob for press molding is as follows.
- the molten glass flowing out from the pipe is continuously cast into a mold horizontally disposed below the outflow pipe, and formed into a plate shape having a certain thickness.
- the molded glass is continuously pulled out in the horizontal direction from an opening provided on the side surface of the mold.
- the sheet glass molded body is pulled out by a belt conveyor.
- a glass molded body having a predetermined thickness and plate width can be obtained by pulling out the glass molded body so that the plate thickness of the glass molded body is constant at a constant belt conveyor drawing speed.
- the glass molded body is conveyed into an annealing furnace by a belt conveyor and gradually cooled.
- the slowly cooled glass molded body is cut or cleaved in the plate thickness direction and polished or barrel-polished to form a glass gob for press molding.
- molten glass is cast into a cylindrical mold instead of the above mold to form a columnar glass molded body.
- the glass molded body molded in the mold is drawn vertically downward from the opening at the bottom of the mold at a constant speed.
- the drawing speed may be set so that the molten glass liquid level in the mold becomes constant. After slowly cooling the glass molded body, it is cut or cleaved, and subjected to polishing or barrel polishing to obtain a glass gob for press molding.
- a molding machine in which a plurality of molding dies are arranged at equal intervals on the circumference of a circular turntable is installed below the outflow pipe, the turntable is index-rotated, and the molding die is stopped.
- One of the positions is the position where the molten glass is supplied to the mold (referred to as the cast position), the molten glass is supplied, the supplied molten glass is formed into a glass molded body, and then the predetermined mold different from the cast position is retained.
- the glass molded body is taken out from the position (takeout position).
- the stop position as the take-out position may be determined in consideration of the rotation speed of the turntable, the cooling speed of the glass, and the like.
- the molten glass is supplied to the mold at the casting position by dropping molten glass from the glass outlet of the outflow pipe and receiving the glass droplets at the above-mentioned mold, and by bringing the molding mold retained at the casting position closer to the glass outlet. Supports the lower end of the flowing molten glass flow, creates a constriction in the middle of the glass flow, and rapidly drops the mold in the vertical direction at a predetermined timing to separate the molten glass below the constriction and receive it on the mold It can be performed by a method, a method in which the flowing molten glass flow is cut with a cutting blade, and the separated molten glass lump is received by a mold that is retained at the casting position. A known method may be used to form the glass on the mold.
- the shape of the glass molded body is spherical, spheroid, and has one rotation target axis depending on the selection of the mold shape and the gas ejection method, and two surfaces facing the axis direction of the rotation target axis. Can be formed into a shape that is convex outward. These shapes are suitable for a glass gob for press molding an optical element such as a lens or an optical element blank.
- the glass molded body thus obtained can be used as it is, or the surface can be polished or barrel-polished to form a glass gob for press molding.
- optical element blank is made of the optical glass according to one aspect of the present invention described above.
- the optical element blank according to one aspect of the present invention is suitable as a glass base material for producing an optical element having various properties provided by the optical glass according to one aspect of the present invention.
- the optical element blank is a glass molded body having a shape approximate to the shape of the optical element obtained by adding a processing margin to be removed by grinding and polishing to the shape of the target optical element.
- a first aspect of the method for manufacturing an optical element blank is a method for manufacturing an optical element blank that is finished into an optical element by grinding and polishing.
- the press molding glass gob according to one aspect of the present invention is softened by heating and pressed. Mold. This method is also called a reheat press molding method.
- the glass raw material is melted by heating, and the obtained molten glass is press-molded.
- the optical element blank according to one embodiment of the present invention is manufactured. This method is also called a direct press molding method.
- a press mold having a molding surface having a shape approximating a shape obtained by inverting the surface shape of the target optical element is prepared.
- the press mold is composed of mold parts including an upper mold, a lower mold, and, if necessary, a barrel mold.
- the glass gob for press molding is softened by heating and then introduced into a preheated lower mold, pressed with the upper mold facing the lower mold, and molded into an optical element blank.
- a powder release agent such as boron nitride may be uniformly applied to the surface of the glass gob for press molding in advance.
- the optical element blank is released, removed from the press mold, and annealed.
- the distortion inside the glass is reduced so that the optical characteristics such as the refractive index become a desired value.
- the glass gob heating conditions, press molding conditions, materials used for the press mold, and the like may be applied. The above steps can be performed in the atmosphere.
- the press mold is composed of mold parts including an upper mold, a lower mold, and, if necessary, a barrel mold.
- the molding surface of the press mold is processed into a shape obtained by inverting the surface shape of the optical element blank.
- a powder mold release agent such as boron nitride is uniformly applied onto the lower mold surface as appropriate, and the molten glass melted according to the optical glass manufacturing method described above flows out onto the lower mold surface, When the amount of molten glass reaches a desired amount, the molten glass flow is cut with a cutting blade called shear.
- the lower mold After obtaining a molten glass lump on the lower mold in this manner, the lower mold is moved together with the molten glass lump to a position where the upper mold waits upward, and the glass is pressed with the upper mold and the lower mold to form an optical element blank. .
- the optical element blank is released, removed from the press mold, and annealed. By this annealing treatment, the distortion inside the glass is reduced so that the optical characteristics such as the refractive index become a desired value.
- the glass gob heating conditions, press molding conditions, materials used for the press mold, and the like may be applied. The above steps can be performed in the atmosphere.
- optical element Next, an optical element according to one embodiment of the present invention will be described.
- the optical element according to one aspect of the present invention is made of the optical glass according to one aspect of the present invention described above.
- the optical element according to one embodiment of the present invention has various properties that the above-described optical glass according to one embodiment of the present invention can provide, and thus is effective in increasing the functionality and compactness of the optical system.
- Examples of the optical element of the present invention include various lenses and prisms.
- examples of the lens include various lenses such as a concave meniscus lens, a convex meniscus lens, a biconvex lens, a biconcave lens, a planoconvex lens, and a planoconcave lens, whose lens surface is spherical or aspherical.
- Such a lens can correct chromatic aberration when combined with a lens made of ultra-low dispersion glass, and is suitable as a lens for correcting chromatic aberration. It is also an effective lens for making the optical system compact. Since the optical element according to one embodiment of the present invention is made of glass having a smaller ⁇ Pg, F than optical glass having an equivalent refractive index and Abbe number, it is suitable for higher-order chromatic aberration correction.
- a compact optical system when combined with a lens made of ultra-low dispersion glass having positive anomalous partial dispersion, high-order chromatic aberration correction can be realized with a compact optical system.
- the prism since the prism has a high refractive index, a compact optical system with a wide angle of view can be realized by incorporating the prism into the imaging optical system and bending the optical path in a desired direction.
- a film for controlling light transmittance such as an antireflection film, may be provided on the optical functional surface of the optical element according to one embodiment of the present invention.
- the optical element can be produced by processing the above-described optical element blank. Since the optical glass which comprises an optical element blank can use what was excellent in workability, as a processing method, a well-known method is applicable.
- optical glass according to one embodiment of the present invention can be obtained by applying the method for adjusting the content of each glass component described above with reference to the examples described below.
- oxide glass No. 1 having the composition shown in Table 1 (expressed as cation%).
- nitrates, sulfates, hydroxides, oxides, boric acid, etc. are used as raw materials.
- Each raw material powder is weighed and thoroughly mixed to prepare a mixed raw material.
- This mixed raw material is made of platinum. It put in the crucible or the crucible made from a platinum alloy, and it heated and melted at 1400 degreeC, clarified and stirred, and made the homogeneous molten glass.
- the molten glass was poured into a preheated mold and rapidly cooled, held at a temperature in the vicinity of the glass transition temperature for 2 hours, and then slowly cooled to obtain oxide glass no. 1 to 22 optical glasses were obtained. In any glass, no precipitation of crystals or inclusion of foreign matters such as platinum inclusions was observed.
- oxide glass No. The total amount of anionic components 1 to 15 is O 2 ⁇ .
- the constants (A 0 , A 1 , A 2 , A 3 , A 4 , A 5 ) of the following dispersion formula (x) were calculated by the least square method using these refractive indexes. Using the calculated constants, ng, nF, and nC were calculated from the following dispersion formula (x) to obtain Pg and F.
- n 2 A 0 + A 1 ⁇ 2 + A 2 ⁇ ⁇ 2 + A 3 ⁇ ⁇ 4 + A 4 ⁇ ⁇ 6 + A 5 ⁇ ⁇ 8 (x)
- the difference ⁇ Pg, F of the partial dispersion ratio from the normal line was calculated from the partial dispersion ratio Pg, F (0) on the normal line calculated from the partial dispersion ratio Pg, F and the Abbe number ⁇ d.
- Glass transition temperature Tg Using a thermomechanical analyzer, the measurement was performed under the condition of a heating rate of 4 ° C./min. (4) Bending point It measured using the thermomechanical analyzer on the conditions of the temperature increase rate of 4 degree-C / min.
- Liquidus temperature The glass was placed in a furnace heated to a predetermined temperature and held for 2 hours. After cooling, the inside of the glass was observed with a 100-fold optical microscope, and the liquidus temperature was determined from the presence or absence of crystals.
- (7) ⁇ 70, ⁇ 5 A glass sample having parallel surfaces polished to a thickness of 10.0 ⁇ 0.1 mm is used, and a spectrophotometer is used to inject light having an intensity Iin from a direction perpendicular to the polished surface. The light transmittance Iout / Iin was calculated by measuring the intensity Iout of the light transmitted through the light. The wavelength at which the light transmittance was 70% was ⁇ 70, and the wavelength at which the light transmittance was 5% was ⁇ 5.
- Example 2 a glass gob for press molding made of each optical glass of Example 1 was produced as follows. First, glass raw materials were prepared so as to obtain the above-described glasses, put into a platinum crucible or a platinum alloy crucible, heated, melted, clarified and stirred to obtain a homogeneous molten glass. Next, the molten glass was flown out from the outflow pipe at a constant flow rate and cast into a mold placed horizontally below the outflow pipe to form a glass plate having a constant thickness. The formed glass plate was continuously pulled out from the opening provided on the side surface of the mold in the horizontal direction, conveyed to the annealing furnace by a belt conveyor, and gradually cooled.
- the slowly cooled glass plate was cut or cleaved to produce glass pieces, and these glass pieces were barrel-polished into glass gob for press molding.
- a cylindrical mold is disposed below the outflow pipe, molten glass is cast into the mold to form a cylindrical glass, and is drawn vertically downward from the opening at the bottom of the mold at a constant speed. Glass pieces can be obtained by cooling, cutting or cleaving to make glass pieces, and barrel-polishing these glass pieces.
- Example 3 In the same manner as in Example 2, after the molten glass flows out from the outflow pipe and receives the lower end of the molten glass flowing out from the mold, the mold is rapidly lowered, the molten glass flow is cut by the surface tension, and the desired shape is placed on the mold. An amount of molten glass ingot was obtained. Then, gas was blown out from the mold, an upward wind pressure was applied to the glass, and the glass was molded into a glass lump while being lifted, taken out from the mold and annealed. The glass lump was then barrel-polished to form a glass gob for press molding.
- Example 4 After uniformly applying a release agent composed of boron nitride powder on the entire surface of each press-molding glass gob obtained in Example 3, the gob was softened by heating and press-molded, and a concave meniscus lens, a convex meniscus lens, Various lenses such as a biconvex lens, a biconcave lens, a planoconvex lens, and a planoconcave lens, and a prism blank were prepared.
- Example 5 A molten glass was produced in the same manner as in Example 2, and the molten glass was supplied to the lower mold forming surface uniformly coated with a release agent of boron nitride powder, and when the amount of molten glass on the lower mold reached a desired amount. The molten glass stream was cut with a cutting blade. The molten glass block thus obtained on the lower mold was pressed with the upper mold and the lower mold, and a concave meniscus lens, a convex meniscus lens, a biconvex lens, a biconcave lens, a plano-convex lens, a plano-concave lens, etc., and a prism blank were produced. .
- Example 6 Each blank produced in Examples 4 and 5 was annealed. The annealing reduced the internal distortion of the glass, and the optical characteristics such as the refractive index were set to desired values. Each blank was then ground and polished to produce various lenses and prisms such as a concave meniscus lens, a convex meniscus lens, a biconvex lens, a biconcave lens, a planoconvex lens, and a planoconcave lens. The surface of the obtained optical element may be coated with an antireflection film.
- Example 7 A glass plate and a columnar glass were produced in the same manner as in Example 2, and the obtained glass molded body was annealed to reduce internal strain and to make optical characteristics such as refractive index have desired values. Next, these glass moldings were cut, ground and polished to prepare concave meniscus lenses, convex meniscus lenses, biconvex lenses, biconcave lenses, planoconvex lenses, planoconcave lenses, and other lenses, and prism blanks. An antireflection film may be coated on the surface of the obtained optical element.
- an optical glass having high refractive index and low dispersibility suitable as an optical element material for color correction correction having stable glass supply and excellent glass stability. Furthermore, a glass gob for press molding, an optical element blank, and an optical element can be provided using the optical glass.
- FIGS. 1 and 2 show the cation ratio (Y 3+ / (La 3+ + Gd 3+ + Y 3+ + Yb 3+ )) . )) Is a digital camera photograph showing that an optical glass having a value exceeding 0.180 is inferior in glass stability. Details will be described below with reference to FIGS.
- the optical glasses A and B shown in Table 2 have a composition in which the cation ratio (Y 3+ / (La 3+ + Gd 3+ + Y 3+ + Yb 3+ )) exceeds 0.180.
- optical glasses A and B were obtained in Example 7 of JP-A-60-131845, except that Sb 2 O 3 was used instead of As 2 O 3 which is a component that should be avoided due to environmental considerations. 8 glass composition. Note that the devitrification resistance of the glass is hardly affected by changing the fining agent from As 2 O 3 to Sb 2 O 3 .
- Optical glasses A and B were prepared according to the description in the examples of the publication.
- FIG. 1 is a digital camera photograph of the optical glass A in the crucible
- FIG. 2 is a digital camera photograph of the optical glass B dropped on paper.
- the optical glasses A and B were both crystallized, and it was not possible to obtain a homogeneous glass.
- FIG. 3 shows ⁇ Pg, F calculated from the above formula for the optical glass shown in Table 1, the example of US2011 / 0028300A1, and the example of JP2010-083705A. It is the graph plotted with respect to (nu) d.
- the partial dispersion of ⁇ Pg, F is 0.0005 or less with low dispersion characteristics in which the Abbe number ⁇ d is in the range of 28.0 to 34.0. It can be confirmed from FIG. 3 that it does not have characteristics.
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Abstract
Description
このような高屈折率低分散ガラスの一例が、OPTICAL GLASS Technical Data 2011(HOYA株式会社発行)に記載されているHOYA株式会社製光学ガラス(硝種TAFD25(屈折率nd 1.90366、アッベ数νd 31.32))である。
上記の光学ガラスTAFD25は、高屈折率低分散ガラスでありながら、着色が極めて少ないという非常に優れたガラス材料である。しかし、上記ΔPg,Fが0.0028であり、高次の色収差を補正するためには、ΔPg,Fが一層小さい光学ガラスが望まれる。
また、高屈折率低分散ガラスは、特開昭60-131845号公報または英語ファミリーメンバー米国特許第4,584,279号、US2011/0028300A1、特開2010-083705号公報または英語ファミリーメンバーUS2012/0142517A1、米国特許第8,127,570号、それらの全記載は、ここに特に開示として援用される、にも開示されている。
Si4+およびB3+の合計含有量が10~60カチオン%の範囲であり、
La3+、Gd3+、Y3+およびYb3+の合計含有量が25~70カチオン%の範囲であり、
Ti4+、Nb5+、W6+およびBi3+の合計含有量が10~20カチオン%の範囲であり、
Li+含有量が0~5.0カチオン%の範囲であり、
Ge含有量が、酸化物基準のガラス組成におけるGeO2量として5.0質量%未満であり、
Pbを含まず、
B3+含有量に対するSi4+含有量のカチオン比(Si4+/B3+)が0.70以下であり、
Ti4+、Nb5+、W6+およびBi3+の合計含有量に対するLa3+、Gd3+、Y3+およびYb3+の合計含有量のカチオン比((La3++Gd3++Y3++Yb3+)/(Ti4++Nb5++W6++Bi3+))が1.90~7.00の範囲であり、
La3+、Gd3+、Y3+およびYb3+の合計含有量に対するY3+含有量のカチオン比(Y3+/(La3++Gd3++Y3++Yb3+))が0.180以下であり、
Nb5+を必須成分として含み、かつNb5+含有量に対するTi4+含有量のカチオン比(Ti4+/Nb5+)が4.00以下である酸化物ガラスであり、かつ、
屈折率ndが1.920超かつ2.000以下の範囲であり、アッベ数νdが28.0~34.0の範囲であり、屈伏点が645℃超であり、
下記式:
ΔPg,F=Pg,F+(0.0018×νd)-0.6483
[式中、Pg,Fは、g線、F線、c線における各屈折率ng、nF、nCを用いて、(ng-nF)/(nF-nC)で表される部分分散比を表し、νdはアッベ数を表す。]
により求められる部分分散比Pg,Fのノーマルラインからの偏差ΔPg,Fが0.0005以下である光学ガラス、
に関する。
カチオン%表示にて、
Si4+およびB3+を合計で10~60%、
La3+、Gd3+、Y3+およびYb3+を合計で25~70%、
Ti4+、Nb5+、W6+およびBi3+を合計で10~20%、
含み、
Ti4+、Nb5+、W6+およびBi3+の合計含有量に対するLa3+、Gd3+、Y3+およびYb3+の合計含有量のカチオン比((La3++Gd3++Y3++Yb3+)/(Ti4++Nb5++W6++Bi3+))が1.90~7.00である酸化物ガラスであり、かつ、
屈折率ndが1.88~2.00の範囲であり、アッベ数νdが28.0~34.0の範囲であり、下記式:
ΔPg,F=Pg,F+(0.0018×νd)-0.6483
[式中、Pg,Fは、g線、F線、c線における各屈折率ng、nF、nCを用いて、(ng-nF)/(nF-nC)で表される部分分散比を表し、νdはアッベ数を表す。]
により求められる部分分散比Pg,Fのノーマルラインからの偏差ΔPg,Fが0.0005以下である光学ガラス、
に関する。
本発明の一態様は、
Si4+およびB3+の合計含有量が10~60カチオン%の範囲であり、
La3+、Gd3+、Y3+およびYb3+の合計含有量が25~70カチオン%の範囲であり、
Ti4+、Nb5+、W6+およびBi3+の合計含有量が10~20カチオン%の範囲であり、
Li+含有量が0~5.0カチオン%の範囲であり、
Ge含有量が、酸化物基準のガラス組成におけるGeO2量として5.0質量%未満であり、
Pbを含まず、
B3+含有量に対するSi4+含有量のカチオン比(Si4+/B3+)が0.70以下であり、
Ti4+、Nb5+、W6+およびBi3+の合計含有量に対するLa3+、Gd3+、Y3+およびYb3+の合計含有量のカチオン比((La3++Gd3++Y3++Yb3+)/(Ti4++Nb5++W6++Bi3+))が1.90~7.00の範囲であり、
La3+、Gd3+、Y3+およびYb3+の合計含有量に対するY3+含有量のカチオン比(Y3+/(La3++Gd3++Y3++Yb3+))が0.180以下であり、
Nb5+を必須成分として含み、かつNb5+含有量に対するTi4+含有量のカチオン比(Ti4+/Nb5+)が4.00以下である酸化物ガラスであり、かつ、
屈折率ndが1.920超かつ2.000以下の範囲であり、アッベ数νdが28.0~34.0の範囲であり、屈伏点が645℃超であり、
下記式:
ΔPg,F=Pg,F+(0.0018×νd)-0.6483
[式中、Pg,Fは、g線、F線、c線における各屈折率ng、nF、nCを用いて、(ng-nF)/(nF-nC)で表される部分分散比を表し、νdはアッベ数を表す。]
により求められる部分分散比Pg,Fのノーマルラインからの偏差ΔPg,Fが0.0005以下である光学ガラスに関する。
ガラスの熱的安定性の改善、熔融ガラスの成形に適した粘性の実現、化学的耐久性の改善といった観点から、カチオン比(Si4+/B3+)は0.05以上とすることが好ましく、0.1以上とすることがより好ましい。
所望の光学ガラスを得る上から、La3+、Gd3+、Y3+およびYb3+の合計含有量(La3++Gd3++Y3++Yb3+)とTi4+、Nb5+、W6+およびBi3+の合計含有量(Ti4++Nb5++W6++Bi3+)をそれぞれ上記範囲にすることに加え、Ti4+、Nb5+、W6+およびBi3+の合計含有量に対するLa3+、Gd3+、Y3+およびYb3+の合計含有量のカチオン比((La3++Gd3++Y3++Yb3+)/(Ti4++Nb5++W6++Bi3+))を所定の範囲にする。カチオン比((La3++Gd3++Y3++Yb3+)/(Ti4++Nb5++W6++Bi3+))が1.90未満ではΔPg.Fが増加し、耐失透性が悪化し、ガラスの着色が強まる。一方、前記カチオン比が7.00を超えると、耐失透性が悪化し、液相温度が上昇する。したがって、カチオン比((La3++Gd3++Y3++Yb3+)/(Ti4++Nb5++W6++Bi3+))の範囲を1.90~7.00とする。カチオン比((La3++Gd3++Y3++Yb3+)/(Ti4++Nb5++W6++Bi3+))の好ましい上限は6.00、より好ましい上限は5.00、さらに好ましい上限は4.00、一層好ましい上限は3.50、より一層好ましい上限は3.00、さらに一層好ましい上限は2.85であり、前記カチオン比の好ましい下限は1.95、より好ましい下限は1.98、さらに好ましい下限は2.00、一層好ましい下限は2.03、より一層好ましい下限は2.05、さらに一層好ましい下限は2.10である。
上記の観点から、カチオン比(Y3+/(La3++Gd3++Y3++Yb3+))は、好ましくは0.150以下、より好ましくは0.130以下、さらに好ましくは0.100以下である。
カチオン比(Y3+/(La3++Gd3++Y3++Yb3+))を0にすることもできるが、
少量のY3+を含有させることにより、液相温度を低下させ、耐失透性を改善することができることから、カチオン比(Y3+/(La3++Gd3++Y3++Yb3+))は、好ましくは0.020以上である。
ここで、部分分散比Pg,Fは、g線、F線、c線における各屈折率ng、nF、nCを用いて、(ng-nF)/(nF-nC)と表される。本発明におけるng、nF、およびnCは、後述する実施例で示す方法により求められた値とする。
本発明では、高次の色収差補正に好適な光学ガラスを提供する上から、ΔPg,Fを0.0005以下とする。
部分分散比Pg,F-アッベ数νd図において、正常部分分散ガラスの基準となるノーマルライン上の部分分散比をPg,F(0)と表すと、Pg,F(0)はアッベ数νdを用いて次式で表される。
Pg,F(0)=0.6483-(0.0018×νd)
ΔPg,Fは、上記ノーマルラインからの部分分散比Pg,Fの偏差であり、次式で表される。
ΔPg,F=Pg,F-Pg,F(0)
=Pg,F+(0.0018×νd)-0.6483
高次の色収差補正用の光学素子材料として好適な光学ガラスを提供する上から、ΔPg,Fの好ましい範囲は0.0004以下、より好ましい範囲は0.0003以下、さらに好ましい範囲は0.0002以下、一層好ましい範囲は0.0001以下、より一層好ましい範囲は0.0000以下である。
・Si4+およびB3+の合計含有量に対するLa3+、Gd3+、Y3+およびYb3+の合計含有量のカチオン比[(La3++Gd3++Y3++Yb3+)/(Si4++B3+)]を0.83以上とすること、
・Si4+およびB3+の合計含有量に対するTi4+、Nb5+、W6+およびBi3+の合計含有量のカチオン比[(Ti4++Nb5++W6++Bi3+)/(Si4++B3+)]を0.31以上にすること、
の少なくとも一方を満たすこと、または両方を満たすことを挙げることができる。
カチオン比[(La3++Gd3++Y3++Yb3+)/(Si4++B3+)]のより好ましい下限は0.84、さらに好ましい下限は0.85、一層好ましい下限は0.86である。
カチオン比[(Ti4++Nb5++W6++Bi3+)/(Si4++B3+)]のより好ましい下限は0.34、さらに好ましい下限は0.35、一層好ましい下限は0.36、より一層好ましい下限は0.37、さらに一層好ましい下限は0.38、なお一層好ましい下限は0.39である。
カチオン比[(La3++Gd3++Y3++Yb3+)/(Si4++B3+)]の上限は、本発明の一態様にかかる光学ガラスが有するべきガラス組成から自ずと定まるが、例えば2.0以下とすることができる。ガラスの熱的安定性を維持する上から、カチオン比[(La3++Gd3++Y3++Yb3+)/(Si4++B3+)]の好ましい上限は1.6、より好ましい上限は1.4、さらに好ましい上限は1.2、一層好ましい上限は1.0、より一層好ましい上限は0.98である。
また、カチオン比[(Ti4++Nb5++W6++Bi3+)/(Si4++B3+)]の上限も、本発明の一態様にかかる光学ガラスが有するべきガラス組成から自ずと定まるが、例えば1.5以下とすることができる。とすることができる。ガラスの熱的安定性を維持する上から、カチオン比[(Ti4++Nb5++W6++Bi3+)/(Si4++B3+)]の好ましい上限は1.2、より好ましい上限は1.0、さらに好ましい上限は0.8、一層好ましい上限は0.7、より一層好ましい上限は0.6、さらに一層好ましい上限は0.5である。
効果を高める上から、Gd3+、Y3+およびYb3+の合計含有量を0.5%以上とすることが好ましく、1%以上、詳しくは1.0%以上とすることがより好ましく、2%以上、詳しくは2.0%以上とすることがさらに好ましく、3%以上、詳しくは3.0%以上とすることが一層好ましく、4%以上とすることがより一層好ましく、5%以上とすることがさらに一層好ましく、5.5%以上とすることがなお一層好ましい。一方、耐失透性を維持し、液相温度の上昇を抑制する上から、Gd3+、Y3+およびYb3+の合計含有量を35%以下、詳しくは35.0%以下とすることが好ましく、30%以下、詳しくは30.0%以下とすることがより好ましく、25%以下、詳しくは25.0%以下とすることがさらに好ましく、20%以下、詳しくは20.0%以下とすることが一層好ましく、15%以下、詳しくは15.0%以下とすることがより一層好ましく、10%以下、詳しくは10.0%以下とすることがさらに一層好ましく、7%以下、詳しくは7.0%以下とすることがなお一層好ましい。
また、Ta5+は、Ti4+、Nb5+、W6+、Bi3+と比べ、ΔPg,Fを増加させにくい成分であるものの、希少原料であり、原料費が高い。したがって、安定的に光学ガラスを提供する上からは、Ta5+の含有量を削減することが好ましい。この観点から、Ti4+、Nb5+、W6+、Bi3+およびTa5+の合計含有量に対するTa5+の含有量のカチオン比(Ta5+/(Ti4++Nb5++W6++Bi3++Ta5+))は0.45以下にすることが好ましく、0.40以下にすることがより好ましく、0.30以下にすることがさらに好ましく、0.20以下にすることが一層好ましく、0.10以下にすることがさらに一層好ましく、0.00であることが特に好ましい。
上記の他に、Ce酸化物、硫酸塩、硝酸塩、塩化物、フッ化物を清澄剤として少量、添加することもできる。
また、環境影響に配慮し、As、Pb、U、Th、Cdも導入しないことが好ましい。特に、環境影響への配慮から、本発明の一態様にかかる光学ガラスは、Pbを含まないものとする。
さらに、ガラスの優れた光線透過性を活かす上から、Cu、Cr、V、Fe、Ni、Co、Nd、Tbなどの着色の要因となる物質を導入しないことが好ましい。
なお本明細書および本発明において、「導入しない」、「含有しない」、「構成成分の含有量が0%」とは、この構成成分がガラス成分として導入されないことを意味する。ただし不純物として意図せず混入することは許容するものとする。
高屈折率ガラスは、多量の高屈折率化成分(例えばLa3+(La2O3)、Gd3+(Gd2O3)、Y3+(Y2O3)、Yb3+(Yb2O3)、Ti4+(TiO2)、Nb5+(Nb2O5)、Ta5+(Ta2O5)、W6+(WO6)、Zr4+(ZrO2))を含有するが、これらの成分はいずれも単独での融点が極めて高い。そして、高屈折率化成分の総量が多いと、アルカリ金属成分、アルカリ土類金属成分などの熔融温度を低下させる働きのある成分の総量が相対的に減少し、熔融性、耐失透性が低下するため、均質なガラスを得るためには熔融温度を高めなければならない。
熔融温度が高くなるとガラス融液の侵蝕性が強まり、熔融容器が侵蝕され、容器を構成する材料、例えば白金、白金合金などがガラス融液に溶け込んでガラスを着色させたり、白金異物になったりする。また、熔融温度が高いとB3+などの揮発しやすい成分が揮発して、ガラス組成が経時的に変化し、光学特性が変動するという問題も起こる。
このような問題を解決するには、熔融温度の上昇を抑えればよい。熔融温度範囲は均質なガラス融液が得られる温度域と考えればよく、その温度域の下限は概ね液相温度の上昇・下降に連動して変化すると考えてよい。したがって、液相温度の上昇を抑えることができれば熔融温度の上昇も抑制することができる。
また液相温度の上昇を抑えることができれば、ガラス成形時の失透防止に有効であり、ガラスの粘性も成形に適した範囲に調整することができ、高品質のガラス成形体を作製しやすくなる。
以上より、本発明の一態様にかかる光学ガラスの好ましい態様は、液相温度が1400℃以下のガラスである。液相温度の好ましい上限は1350℃、より好ましい上限は1300℃、さらに好ましい上限は1280℃、一層好ましい上限は1270℃、より一層好ましい上限は1260℃、さらに一層好ましい上限は1200℃である。ただし、液相温度を過剰に低くすると所要の光学特性を維持することが困難になるため、ガラスの安定的製造が可能な範囲で液相温度の下限を設けてもよい。このような観点から液相温度の好ましい下限は1100℃、より好ましい下限は1150℃、さらに好ましい下限は1160℃、一層好ましい下限は1170℃、より一層好ましい下限は1180℃である。
本発明の一態様にかかる光学ガラスは高屈折率ガラスであるが、一般にガラスは高屈折率化すると比重が増加傾向を示す。しかし比重の増加は光学素子の重量増加を招くため好ましくない。これに対し本発明の一態様にかかる光学ガラスは、上記ガラス組成を有することにより、高屈折率ガラスでありながら比重を6.00以下にすることができる。ただし、比重を過剰に減少させるとガラスの安定性が低下し、液相温度が上昇する傾向を示すため、比重は4.00以上とすることが好ましい。比重のより好ましい上限は5.50、さらに好ましい上限は5.30、一層好ましい上限は5.20、より一層好ましい上限は5.15である。比重のより好ましい下限は4.30、さらに好ましい下限は4.50、一層好ましい下限は4.80、より一層好ましい下限は4.90である。
次に、本発明の一態様にかかる光学ガラスの光線透過性について説明する。
本発明の一態様にかかる光学ガラスは、可視域の広い波長域にわたり高い光線透過率を示すことができる。本発明の一態様にかかる光学ガラスの好ましい態様では、λ70が500nm以下の着色度を示す。λ70のより好ましい範囲は480nm以下、さらに好ましい範囲は460nm以下、一層好ましい範囲は440nm以下、より一層好ましい範囲は430nm以下である。λ70の下限は特に限定されるものではないが、λ70を減少させるために高屈折率高分散化成分量を過剰に減少してしまうと、屈折率、アッベ数、耐失透性を維持することが難しくなるので、λ70を過剰に減少させないことが好ましい。このような観点からλ70の好ましい下限は360nm、より好ましい下限は370nm、さらに好ましい下限は380nm、一層好ましい下限は390nm、より一層好ましい下限は400nmである。
ここでλ70とは、波長280~700nmの範囲において光線透過率が70%になる波長のことである。ここで、光線透過率とは、10.0±0.1mmの厚さに研磨された互いに平行な面を有するガラス試料を用い、前記研磨された面に対して垂直方向から光を入射して得られる分光透過率、すなわち、前記試料に入射する光の強度をIin、前記試料を透過した光の強度をIoutとしたときのIout/Iinのことである。分光透過率には、試料表面における光の反射損失も含まれる。また、上記研磨は測定波長域の波長に対し、表面粗さが十分小さい状態に平滑化されていることを意味する。本発明の一態様にかかる光学ガラスは、λ70よりも長波長側の可視域では、光線透過率が70%を超えることが好ましい。
本発明の一態様にかかる光学ガラスは、研磨により平滑な光学機能面を形成するために好適なガラスである。研磨などの冷間加工の適性、すなわち冷間加工性は間接的ながらガラス転移温度と関連がある。ガラス転移温度が低いガラスは冷間加工性よりも精密プレス成形に好適であるのに対し、ガラス転移温度が高いガラスは精密プレス成形よりも冷間加工に好適であって、冷間加工性に優れる。したがって、本発明の一態様にかかる光学ガラスにおいてもガラス転移温度を過剰に低くしないことが好ましく、630℃超にすることが好ましく、640℃以上にすることがより好ましく、650℃以上にすることがさらに好ましく、660℃以上にすることが一層好ましく、670℃以上にすることがより一層好ましく、680℃以上にすることがさらに一層好ましく、690℃以上にすることがさらにより一層好ましい。
ただし、ガラス転移温度が高すぎるとガラスを再加熱、軟化して成形する際の加熱温度が高くなり、成形に使用する金型の劣化が著しくなったり、アニール温度も高温になり、アニール炉の劣化、消耗も著しくなる。したがって、ガラス転移温度は850℃以下とすることが好ましく、800℃以下にすることがより好ましく、750℃以下にすることがさらに好ましい。
例えば、粉体状の化合物原料またはカレット原料を目的のガラス組成に対応して秤量、調合し、白金製または白金合金製の熔融容器内に供給した後、これを加熱することで熔融する。上記原料を十分に熔融してガラス化した後、この熔融ガラスの温度を上昇させて清澄を行う。清澄した熔融ガラスを攪拌器による攪拌によって均質化し、ガラス流出パイプに連続供給、流出し、急冷、固化してガラス成形体を得る。
なお、光学ガラスの熔融温度は1250~1500℃の範囲にすることが、均質、低着色かつ光学特性を含む諸特性の安定したガラスを得る上から望ましい。
Si4+およびB3+を合計で10.0~60.0%、
La3+、Gd3+、Y3+およびYb3+を合計で25.0~70.0%、
Ti4+、Nb5+、W6+およびBi3+を合計で10.0~20.0%、
含み、
Ti4+、Nb5+、W6+およびBi3+の合計含有量に対するLa3+、Gd3+、Y3+およびYb3+の合計含有量のカチオン比((La3++Gd3++Y3++Yb3+)/(Ti4++Nb5++W6++Bi3+))が1.90~7.00である酸化物ガラスであり、かつ、
屈折率ndが1.88~2.00の範囲であり、アッベ数νdが28.0~34.0の範囲であり、下記式:
ΔPg,F=Pg,F+(0.0018×νd)-0.6483
[式中、Pg,Fは、g線、F線、c線における各屈折率ng、nF、nCを用いて、(ng-nF)/(nF-nC)で表される部分分散比を表し、νdはアッベ数を表す。]
により求められる部分分散比Pg,Fのノーマルラインからの偏差ΔPg,Fが0.0005以下である光学ガラス、
も提供される。詳細については、上述の本発明の一態様にかかる光学ガラスに関する記載を参照できる。
本発明の一態様にかかるプレス成形用ガラスゴブは前記した本発明の一態様にかかる光学ガラスからなる。ゴブの形状は、目的とするプレス成形品の形状に応じてプレス成形しやすい形状にすることが好ましい。また、ゴブの質量もプレス成形品に合わせて設定することが好ましい。本発明においては、安定性に優れたガラスを使用することができるので、再加熱、軟化してプレス成形してもガラスが失透しにくく、高品質の成形品を安定して生産することができる。
第1の製造例においては、流出パイプの下方に水平に配置した鋳型にパイプから流出する熔融ガラスを連続的に鋳込み、一定の厚みを有する板状に成形する。成形されたガラスは鋳型側面に設けた開口部から水平方向へと連続して引き出される。板状ガラス成形体の引き出しはベルトコンベアによって行う。ベルトコンベアの引き出し速度を一定にしてガラス成形体の板厚が一定になるように引き出すことにより、所定の厚み、板幅のガラス成形体を得ることができる。ガラス成形体はベルトコンベアによりアニール炉内へと搬送され、徐冷される。徐冷したガラス成形体を板厚方向に切断あるいは割断し、研磨加工を施したり、バレル研磨を施してプレス成形用ガラスゴブにする。
成形型上でのガラスの成形は公知の方法を用いればよい。中でも成形型から上向きにガスを噴出してガラス塊に上向きの風圧を加え、ガラスを浮上させながら成形すると、ガラス成形体の表面にシワができたり、成形型との接触によってガラス成形体にカン割れが発生することを防止することができる。
次に本発明の一態様にかかる光学素子ブランクについて説明する。
本発明の一態様にかかる光学素子ブランクは、前記した本発明の一態様にかかる光学ガラスからなる。本発明の一態様にかかる光学素子ブランクは、前記した本発明の一態様にかかる光学ガラスが供える諸性質を有する光学素子を作製するためのガラス母材として好適である。
なお、光学素子ブランクは、目的とする光学素子の形状に、研削および研磨により除去する加工しろを加えた光学素子の形状に近似する形状を有するガラス成形体である。
次にプレス成形用ガラスゴブを加熱により軟化してから予熱された下型に導入し、下型と対向する上型とでプレスし、光学素子ブランクに成形する。このとき、プレス成形時のガラスと成形型の融着を防ぐため、プレス成形用ガラスゴブの表面に予め窒化ホウ素などの粉末状離型剤を均一に塗布してもよい。
次に光学素子ブランクを離型してプレス成形型から取り出し、アニール処理する。このアニール処理によってガラス内部の歪を低減し、屈折率などの光学特性が所望の値になるようにする。
ガラスゴブの加熱条件、プレス成形条件、プレス成形型に使用する材料などは公知のものを適用すればよい。以上の工程は大気中で行うことができる。
下型成形面上に適宜、窒化ホウ素などの粉末状離型剤を均一に塗布し、前述の光学ガラスの製造方法にしたがい熔融した熔融ガラスを下型成形面上に流出し、下型上の熔融ガラス量が所望の量になったところで熔融ガラス流をシアと呼ばれる切断刃で切断する。こうして下型上に熔融ガラス塊を得た後、上方に上型が待機する位置に熔融ガラス塊ごと下型を移動し、上型と下型とでガラスをプレスし、光学素子ブランクに成形する。
次に光学素子ブランクを離型してプレス成形型から取り出し、アニール処理する。このアニール処理によってガラス内部の歪を低減し、屈折率などの光学特性が所望の値になるようにする。
ガラスゴブの加熱条件、プレス成形条件、プレス成形型に使用する材料などは公知のものを適用すればよい。以上の工程は大気中で行うことができる。
次に本発明の一態様にかかる光学素子について説明する。
本発明の一態様にかかる光学素子は、前記した本発明の一態様にかかる光学ガラスからなる。本発明の一態様にかかる光学素子は、前記した本発明の一態様にかかる光学ガラスが供える諸性質を有するため、光学系の高機能化、コンパクト化に有効である。本発明の光学素子としては、各種レンズ、プリズムなどを例示することができる。さらにレンズの例としては、レンズ面が球面または非球面である、凹メニスカスレンズ、凸メニスカスレンズ、両凸レンズ、両凹レンズ、平凸レンズ、平凹レンズなどの各種レンズを示すことができる。
こうしたレンズは、超低分散ガラス製のレンズと組み合わせることにより色収差を補正することができ、色収差補正用のレンズとして好適である。また、光学系のコンパクト化にも有効なレンズである。本発明の一態様にかかる光学素子は、同等の屈折率、アッベ数を有する光学ガラスよりもΔPg,Fが小さいガラスにより作製されているため、高次の色収差補正に好適である。例えば、正の異常部分分散性を有する超低分散ガラス製のレンズと組み合わせることにより、高次の色収差補正をコンパクトな光学系で実現することができる。
また、プリズムについては、屈折率が高いので撮像光学系に組み込むことにより、光路を曲げて所望の方向に向けることによりコンパクトで広い画角の光学系を実現することもできる。
なお本発明の一態様にかかる光学素子の光学機能面には、反射防止膜などの光線透過率を制御する膜を設けることもできる。
上記光学素子は、前記した光学素子ブランクを加工することにより作製することができる。光学素子ブランクを構成する光学ガラスとして加工性に優れたものを使用することができるので、加工方法としては、公知の方法を適用することができる。
まず、表1示す組成(カチオン%表示)を有する酸化物ガラスNo.1~22が得られるように、原料として硝酸塩、硫酸塩、水酸化物、酸化物、ホウ酸などを用い、各原料粉末を秤量して十分混合し、調合原料とし、この調合原料を白金製坩堝または白金合金製坩堝に入れて1400℃で加熱、熔融し、清澄、撹拌して均質な熔融ガラスした。
この熔融ガラスを予熱した鋳型に流し込んで急冷し、ガラス転移温度近傍の温度で2時間保持した後、徐冷して酸化物ガラスNo.1~22の各光学ガラスを得た。いずれのガラス中にも結晶の析出や白金インクルージョンなどの異物の混入は認められなかった。
なお、酸化物ガラスNo.1~15のアニオン成分は全量、O2-である。
(1)屈折率ndおよびアッベ数νd
1時間あたり30℃の降温速度で冷却した光学ガラスについて測定した。
(2)部分分散比Pg,F、部分分散比のノーマルラインからの差ΔPg,F
部分分散比Pg,Fは、1時間あたり30℃の降温速度で冷却した光学ガラスについて下記方法により屈折率ng、nF、nCを測定し、これらの値から算出した。
t(1013.98nm)、s(852.11nm)、A’(768.19nm)、r(706.52nm)、C(656.27nm)、C’(643.85nm)、632.8(632.8nm)、D(589.29nm)、d(587.56nm)、e(546.07nm)、F(486.13nm)、F’(479.99nm)、g(435.84nm)、h(404.66nm)、およびi(365.01nm)の計15線について各波長λにおける屈折率nを測定した。
これらの屈折率を用いて最小二乗法により下記分散式(x)の定数(A0、A1、A2、A3、A4、A5)を算出した。算出した定数を用いて下記分散式(x)から、ng,nF,nCを算出し、Pg,Fを求めた。
n2=A0+A1λ2+A2λ-2+A3λ-4+A4λ-6+A5λ-8 (x)
部分分散比のノーマルラインからの差ΔPg,Fは、部分分散比Pg,Fおよびアッベ数νdから算出されるノーマルライン上の部分分散比Pg,F(0)から算出した。
(3)ガラス転移温度Tg
熱機械分析装置を用いて、昇温速度4℃/分の条件下で測定した。
(4)屈伏点
熱機械分析装置を用いて、昇温速度4℃/分の条件下で測定した。
(5)液相温度
ガラスを所定温度に加熱された炉内に入れて2時間保持し、冷却後、ガラス内部を100倍の光学顕微鏡で観察し、結晶の有無から液相温度を決定した。
(6)比重
アルキメデス法により測定した。
(7)λ70、λ5
10.0±0.1mmの厚さに研磨された互いに平行な面を有するガラス試料を用い、分光光度計により、前記研磨された面に対して垂直方向から強度Iinの光を入射し、試料を透過した光の強度Ioutを測定し、光線透過率Iout/Iinを算出し、光線透過率が70%になる波長をλ70、光線透過率が5%になる波長をλ5とした。
次に実施例1の各光学ガラスからなるプレス成形用ガラスゴブを次のようにして作製した。
まず、上記各ガラスが得られるようにガラス原料を調合し、白金製坩堝または白金合金製坩堝に投入し、加熱、熔融し、清澄、撹拌して均質な熔融ガラスを得た。次に、熔融ガラスを流出パイプから一定流量で流出し、流出パイプの下方に水平に配置した鋳型に鋳込み、一定の厚みを有するガラス板を成形した。成形されたガラス板を鋳型側面に設けた開口部から水平方向へと連続して引き出し、ベルトコンベアにてアニール炉内へと搬送し、徐冷した。
徐冷したガラス板を切断または割断してガラス片を作製し、これらガラス片をバレル研磨してプレス成形用ガラスゴブにした。
なお、流出パイプの下方に円筒状の鋳型を配置し、この鋳型内に熔融ガラスを鋳込んで円柱状ガラスに成形し、鋳型底部の開口部から一定の速度で鉛直下方に引き出した後、徐冷し、切断もしくは割断してガラス片を作り、これらガラス片をバレル研磨してプレス成形用ガラスゴブを得ることもできる。
実施例2と同様に熔融ガラスを流出パイプから流出し、成形型で流出する熔融ガラス下端を受けた後、成形型を急降下し、表面張力によって熔融ガラス流を切断し、成形型上に所望の量の熔融ガラス塊を得た。そして、成形型からガスを噴出してガラスに上向きの風圧を加え、浮上させながらガラス塊に成形し、成形型から取り出してアニールした。それからガラス塊をバレル研磨してプレス成形用ガラスゴブとした。
実施例3で得た各プレス成形用ガラスゴブの全表面に窒化ホウ素粉末からなる離型剤を均一に塗布した後、上記ゴブを加熱により軟化してプレス成形し、凹メニスカスレンズ、凸メニスカスレンズ、両凸レンズ、両凹レンズ、平凸レンズ、平凹レンズなどの各種レンズ、プリズムのブランクを作製した。
実施例2と同様にして熔融ガラスを作製し、熔融ガラスを窒化ホウ素粉末の離型剤を均一に塗布した下型成形面に供給し、下型上の熔融ガラス量が所望量になったところで熔融ガラス流を切断刃で切断した。
こうして下型上に得た熔融ガラス塊を上型と下型でプレスし、凹メニスカスレンズ、凸メニスカスレンズ、両凸レンズ、両凹レンズ、平凸レンズ、平凹レンズなどの各種レンズ、プリズムのブランクを作製した。
実施例4、5で作製した各ブランクをアニールした。アニールによってガラス内部の歪を低減するとともに、屈折率などの光学特性が所望の値になるようにした。
次に各ブランクを研削および研磨して凹メニスカスレンズ、凸メニスカスレンズ、両凸レンズ、両凹レンズ、平凸レンズ、平凹レンズなどの各種レンズ、プリズムを作製した。得られた光学素子の表面には反射防止膜をコートしてもよい。
実施例2と同様にしてガラス板および円柱状ガラスを作製し、得られたガラス成形体をアニールして内部の歪を低減するとともに、屈折率などの光学特性が所望の値になるようした。
次にこれらガラス成形体を切断、研削および研磨して凹メニスカスレンズ、凸メニスカスレンズ、両凸レンズ、両凹レンズ、平凸レンズ、平凹レンズなどの各種レンズ、プリズムのブランクを作製した。得られた光学素子の表面に反射防止膜をコートしてもよい。
図1、2は、カチオン比(Y3+/(La3++Gd3++Y3++Yb3+))が0.180を超える光学ガラスがガラス安定性に劣ることを示すデジタルカメラ写真である。図1、2ついて、以下に詳細を説明する。
表2に示す光学ガラスA、Bは、カチオン比(Y3+/(La3++Gd3++Y3++Yb3+))が0.180を超える組成を有する。光学ガラスA、Bは、環境への配慮から導入を避けるべき成分であるAs2O3の代わりにSb2O3を用いた点を除き、特開昭60-131845号公報の実施例7、8のガラス組成を有する。なお、清澄剤をAs2O3からSb2O3へ変更することにより、ガラスの耐失透性はほとんど影響を受けることはない。光学ガラスA、Bを、同公報の実施例の記載に忠実にしたがい調製した。図1は、坩堝中の光学ガラスAのデジタルカメラ写真であり、図2は、紙の上に滴下した光学ガラスBのデジタルカメラ写真である。図1、2に示すように、光学ガラスA、Bはいずれも結晶化してしまい、均質なガラスを得ることはできなかった。
図3は、表1に示す光学ガラス、US2011/0028300A1の実施例、および特開2010-083705号公報の実施例について、前述の式から算出されるΔPg,Fを、アッベ数νdに対してプロットしたグラフである。US2011/0028300A1の実施例、および特開2010-083705号公報の実施例とも、アッベ数νdが28.0~34.0の範囲という低分散特性とともに、ΔPg,Fが0.0005以下という部分分散特性を有するものではないことが、図3から確認できる。
Claims (12)
- Si4+およびB3+の合計含有量が10~60カチオン%の範囲であり、
La3+、Gd3+、Y3+およびYb3+の合計含有量が25~70カチオン%の範囲であり、
Ti4+、Nb5+、W6+およびBi3+の合計含有量が10~20カチオン%の範囲であり、
Li+含有量が0~5.0カチオン%の範囲であり、
Ge含有量が、酸化物基準のガラス組成におけるGeO2量として5.0質量%未満であり、
Pbを含まず、
B3+含有量に対するSi4+含有量のカチオン比(Si4+/B3+)が0.70以下であり、
Ti4+、Nb5+、W6+およびBi3+の合計含有量に対するLa3+、Gd3+、Y3+およびYb3+の合計含有量のカチオン比((La3++Gd3++Y3++Yb3+)/(Ti4++Nb5++W6++Bi3+))が1.90~7.00の範囲であり、
La3+、Gd3+、Y3+およびYb3+の合計含有量に対するY3+含有量のカチオン比(Y3+/(La3++Gd3++Y3++Yb3+))が0.180以下であり、
Nb5+を必須成分として含み、かつNb5+含有量に対するTi4+含有量のカチオン比(Ti4+/Nb5+)が4.00以下である酸化物ガラスであり、かつ、
屈折率ndが1.920超かつ2.000以下の範囲であり、アッベ数νdが28.0~34.0の範囲であり、屈伏点が645℃超であり、
下記式:
ΔPg,F=Pg,F+(0.0018×νd)-0.6483
[式中、Pg,Fは、g線、F線、c線における各屈折率ng、nF、nCを用いて、(ng-nF)/(nF-nC)で表される部分分散比を表し、νdはアッベ数を表す。]
により求められる部分分散比Pg,Fのノーマルラインからの偏差ΔPg,Fが0.0005以下である光学ガラス。 - Yb含有量が、酸化物基準のガラス組成におけるYb2O3量として2質量%未満である請求項1に記載の光学ガラス。
- Si4+およびB3+の合計含有量に対するLa3+、Gd3+、Y3+およびYb3+の合計含有量のカチオン比[(La3++Gd3++Y3++Yb3+)/(Si4++B3+)]が0.83以上であるか、または、Si4+およびB3+の合計含有量に対するTi4+、Nb5+、W6+およびBi3+の合計含有量のカチオン比[(Ti4++Nb5++W6++Bi3+)/(Si4++B3+)]が0.31以上である請求項1または2に記載の光学ガラス。
- Ti4+、Nb5+、W6+、Bi3+およびTa5+の合計含有量が13~30カチオン%の範囲である請求項1~3のいずれか1項に記載の光学ガラス。
- Si4+含有量が1.0~30カチオン%の範囲であり、B3+含有量が5~55カチオン%の範囲であり、La3+含有量が10~50%カチオン%の範囲である請求項1~4のいずれか1項に記載の光学ガラス。
- Zr4+含有量が1~15カチオン%の範囲である請求項1~5のいずれか1項に記載の光学ガラス。
- Zn2+含有量が0~15カチオン%の範囲である請求項1~6のいずれか1項に記載の光学ガラス。
- ガラス転移温度が630℃超である請求項1~7のいずれか1項に記載の光学ガラス。
- Gd3+、Y3+およびYb3+の合計含有量が0.5~35カチオン%の範囲である請求項1~8のいずれか1項に記載の光学ガラス。
- 請求項1~9のいずれか1項に記載の光学ガラスからなるプレス成形用ガラスゴブ。
- 請求項1~9のいずれか1項に記載の光学ガラスからなる光学素子ブランク。
- 請求項1~9のいずれか1項に記載の光学ガラスからなる光学素子。
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