WO2014129510A1 - 光学ガラス、光学ガラスブランク、プレス成型用ガラス素材、光学素子、およびそれらの製造方法 - Google Patents
光学ガラス、光学ガラスブランク、プレス成型用ガラス素材、光学素子、およびそれらの製造方法 Download PDFInfo
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- WO2014129510A1 WO2014129510A1 PCT/JP2014/053945 JP2014053945W WO2014129510A1 WO 2014129510 A1 WO2014129510 A1 WO 2014129510A1 JP 2014053945 W JP2014053945 W JP 2014053945W WO 2014129510 A1 WO2014129510 A1 WO 2014129510A1
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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
- C03C3/16—Silica-free oxide glass compositions containing phosphorus
- C03C3/21—Silica-free oxide glass compositions containing phosphorus containing titanium, zirconium, vanadium, tungsten or molybdenum
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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
-
- 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
- C03C3/097—Glass compositions containing silica with 40% to 90% silica, by weight containing phosphorus, niobium or tantalum
Definitions
- the present invention relates to an optical glass, an optical glass blank, a glass material for press molding, an optical element, and a manufacturing method thereof. Specifically, the present invention relates to a phosphoric acid-based optical glass having a high refractive index and a high dispersion characteristic excellent in devitrification resistance, an optical glass blank made of this optical glass, a glass material for press molding, an optical element, and a method for producing them.
- optical glass containing a large amount of phosphoric acid as a glass network former those having various refractive indexes as described in Patent Documents 1 to 8 are known.
- optical glass having high refractive index and high dispersion characteristics (low Abbe number) is in high demand as an optical element material for various lenses.
- a compact and highly functional optical system for correcting chromatic aberration can be configured by combining with a lens having a high refractive index and low dispersion.
- optical functional surface of a lens having a high refractive index and high dispersion characteristics aspherical, it is possible to further enhance the functions and compactness of various optical systems.
- an optical element such as a lens
- a method of manufacturing an optical element by making an intermediate product called an optical element blank that approximates the shape of the optical element, and grinding and polishing the intermediate product. It has been.
- a method for producing such an intermediate product there is a method (referred to as a direct press method) in which an appropriate amount of molten glass is press-molded to obtain an intermediate product.
- molten glass is cast into a mold and formed into a glass plate, the glass plate is cut into a plurality of glass pieces, and the glass pieces are reheated and softened to form an intermediate product by press molding.
- a method of forming an intermediate product by forming an appropriate amount of molten glass into a glass lump called a glass gob, barrel-polishing the glass lump and then reheating and softening it.
- a method of press-molding by reheating and softening glass is called a reheat press method as opposed to a direct press method.
- a glass material for press molding is produced from molten glass, and the optical element is obtained by precision press molding the glass material for press molding with a molding die (referred to as a precision press molding method).
- a precision press molding method Is also known.
- the optical functional surface of the optical element can be formed without passing through machining such as polishing and grinding by transferring the shape of the molding surface.
- any of the direct press method, the reheat press method, and the precision press molding method described above it is difficult to obtain an optical element having excellent transparency if crystals are precipitated in the glass during the manufacturing process. . Therefore, there is a demand for an optical glass that suppresses crystal precipitation, that is, has high devitrification resistance.
- an optical glass having a composition containing a large amount of phosphoric acid as a glass network former and a high refractive index imparting component and a high dispersibility imparting component generally has a strong tendency to devitrify. Therefore, it has been difficult in the past to improve the devitrification resistance of the phosphoric acid optical glass having a high refractive index and a high dispersion characteristic.
- One embodiment of the present invention provides a phosphoric acid optical glass having high refractive index and high dispersion characteristics and excellent devitrification resistance. Furthermore, according to one aspect of the present invention, an optical glass blank made of the above-described optical glass, a glass material for press molding, an optical element, and methods for producing them are also provided.
- Embodiment 1 is a glass composition based on oxide.
- P 2 O 5 content is 20 to 34% by mass
- B 2 O 3 content is more than 0% by mass and 10% by mass or less
- the mass ratio (B 2 O 3 / P 2 O 5 ) is greater than 0 and less than 0.39
- the mass ratio [TiO 2 / (TiO 2 + Nb 2 O 5 + WO 3 + Bi 2 O 3 + Ta 2 O 5 )] is in the range of 0.059 to 0.180
- the mass ratio [(P 2 O 5 + B 2 O 3 + SiO 2 ) / (Na 2 O + K 2 O + Li 2 O)] is in the range of 1.39 to 1.80
- An optical glass having a refractive index nd in the range of 1.78 to 1.83 and an Abbe number ⁇ d in the range of 20 to 25, About.
- the optical glass according to aspect 1 is a phosphoric acid-based optical glass containing P 2 O 5 as an essential component, further containing B 2 O 3 and TiO 2 as essential components, and satisfying the above-described content and mass ratio. As a result, it has high refractive index and high dispersion characteristics such as a refractive index nd in the range of 1.78 to 1.83 and an Abbe number ⁇ d in the range of 20 to 25, and excellent devitrification resistance.
- An optical glass according to one embodiment of the present invention (hereinafter referred to as “embodiment 2”) is
- P 2 O 5 , B 2 O 3 and TiO 2 are essential components
- SiO 2 , Li 2 O, Nb 2 O 5 , WO 3 , Bi 2 O 3 , and Ta 2 O 5 are optional components
- P 2 O 5 content is 20 to 34% by mass
- B 2 O 3 content is more than 0% by mass and 10% by mass or less
- Li 2 O content is 0 mass% or more and less than 0.3 mass%
- the mass ratio (B 2 O 3 / P 2 O 5 ) is greater than 0 and less than 0.39
- the mass ratio [(P 2 O 5 + B 2 O 3 ) / (TiO 2 + Nb 2 O 5 + WO 3 + Bi 2 O 3 + Ta 2 O 5 )] exceeds 0.53,
- Glasses 2-A and 2-B described above contain P 2 O 5 , B 2 O 3 and TiO 2 as essential components, and include SiO 2 , Li 2 O, Nb 2 O 5 , WO 3 , Bi 2 O 3 , And Ta 2 O 5 can optionally be included.
- P 2 O 5 , B 2 O 3 and TiO 2 as essential components, and include SiO 2 , Li 2 O, Nb 2 O 5 , WO 3 , Bi 2 O 3 , And Ta 2 O 5 can optionally be included.
- it has a high refractive index and high dispersion characteristic of a refractive index nd in the range of 1.78 to 1.83 and an Abbe number ⁇ d in the range of 20 to 25, and an excellent resistance to resistance. It becomes possible to obtain a phosphoric acid optical glass exhibiting devitrification.
- Aspect 1 and Aspect 2 it is possible to provide a phosphate-based optical glass having a high refractive index and a high dispersion characteristic that is suitable for any of the direct press method, the reheat press method, and the precision press molding method.
- an optical element blank made of the above optical glass, a glass material for press molding, and an optical element are also provided.
- the above-described precision press molding method is a method by which an optical element such as an aspherical lens can be efficiently manufactured. Therefore, the above-mentioned phosphoric acid-based optical glass has high refractive index and high dispersion characteristics, as well as properties suitable for precision press molding (good precision press moldability). Desirable for manufacturing.
- one embodiment of the present invention provides a phosphate-based optical glass that has high refractive index and high dispersion characteristics and is suitable for a precision press molding method. Furthermore, according to one aspect of the present invention, there are provided a precision press-molding preform and optical element made of the above-described optical glass, and a method of manufacturing an optical element for precision press-molding the precision press molding preform.
- One embodiment of the present invention is an oxide-based glass composition, 24 to 34% by mass of P 2 O 5 , B 2 O 3 more than 0% by mass and 4% by mass or less, Na 2 O, K 2 O, and Li 2 O in total 12 to 20% by mass, Nb 2 O 5 15-30% by mass, TiO 2 8-15% by mass, Bi 2 O 3 4 to 25% by mass, Including
- the mass ratio (TiO 2 / Nb 2 O 5 ) is in the range of 0.36 to 1.00
- the mass ratio (Bi 2 O 3 / Nb 2 O 5 ) is in the range of 0.16 to 1.67
- the optical glass according to the embodiment 3 includes, as essential components, P 2 O 5 , B 2 O 3, Nb 2 O 5 , TiO 2 , Bi 2 O 3 , alkali metal oxides (Na 2 O, K 2 O, and Li).
- a ratio of TiO 2 and Nb 2 O 5 which are useful components for imparting high refractive index and high dispersion characteristics to the optical glass, and good precision press molding.
- the ratio of Bi 2 O 3 and Nb 2 O 5 which are components capable of imparting properties is defined.
- a phosphoric acid-based optical glass having a high refractive index and a high dispersion characteristic suitable for obtaining a precision press-molding preform.
- a precision press-molding preform and an optical element made of the above-described optical glass are also provided.
- the glass composition of the optical glass is displayed on the basis of oxide.
- the “oxide-based glass composition” refers to a glass composition obtained by converting all glass raw materials to be decomposed during melting and existing as oxides in the optical glass. Unless otherwise specified, the glass composition is displayed on a mass basis.
- the glass composition in the present invention is determined by ICP-AES (Inductively Coupled Plasma-Atomic Emission Spectrometry).
- the analysis value obtained by this analysis method includes a measurement error of about ⁇ 5%.
- the content of the constituent component of 0% means that the constituent component is substantially not included, and that the content of the constituent component is about the impurity level or less. Point to.
- Embodiment 1 Embodiment 2, and Embodiment 3 will be described. Unless otherwise specified, the description relating to one aspect can be applied to another aspect.
- An optical glass corresponding to any two or more of modes 1 to 3 is also included in the optical glass according to one mode of the present invention.
- the optical glass according to aspect 1 has a P 2 O 5 content of 20 to 34% by mass, a B 2 O 3 content of more than 0% by mass and 10% by mass or less in a glass composition based on oxide.
- 2 O 3 / P 2 O 5 is greater than 0 and less than 0.39
- the weight ratio [TiO 2 / (TiO 2 + Nb 2 O 5 + WO 3 + Bi 2 O 3 + Ta 2 O 5)] is from 0.059 to 0.
- the range of 180, the mass ratio [(P 2 O 5 + B 2 O 3 + SiO 2 ) / (Na 2 O + K 2 O + Li 2 O)] is in the range of 1.39 to 1.80, and the refractive index nd Is an optical glass having a range of 1.78 to 1.83 and an Abbe number ⁇ d of 20 to 25. The details will be described below.
- P 2 O 5 is an essential component as a glass forming component in phosphoric acid optical glass.
- Phosphate glass has the characteristics that it can melt glass at a relatively low temperature and has high transmittance in the visible region.
- the lower limit of the P 2 O 5 content is 20% or more, preferably 21% or more.
- an upper limit is 34% or less, Preferably it is 30% or less, More preferably, it is 24% or less.
- B 2 O 3 is a component having an effect of improving devitrification resistance by adding an appropriate amount to phosphoric acid optical glass. Therefore, more than 0% is introduced into the above optical glass as an essential component.
- the B 2 O 3 content is preferably 2% or more, more preferably 6% or more. However, if an excessive amount is included, it is difficult to achieve a high refractive index and a high dispersion characteristic, so the content is made 10% or less. Preferably it is 9% or less, More preferably, it is 8% or less.
- B The 2 O 3 content of 0% including the case where B 2 O 3 is contained in a trace amount to about impurity level in the glass.
- the content of B 2 O 3 greater than 0% refers to the B 2 O 3 is contained in an amount exceeding about impurity levels. Specifically, it is 700 ppm (mass ratio) or more, or 1000 ppm (mass ratio) or more, for example.
- the mass ratio of the P 2 O 5 content to the B 2 O 3 content is more than 0 and less than 0.39.
- a more preferred lower limit is 0.15, and a more preferred lower limit is 0.25.
- a more preferred upper limit is 0.38.
- SiO 2 is an optional component that may be contained in the optical glass described above.
- the content is preferably 2% or less, preferably 1.2% or less, preferably 1.0% or less, and 0.4% or less. More preferably, it is more preferably 0.3% or less, still more preferably less than 0.3%, and it may not be introduced (the SiO 2 content may be 0%).
- the mass ratio of SiO 2 content to the total content of SiO 2 , P 2 O 5 and B 2 O 3 [SiO 2 / (SiO 2 + P 2 O 5 + B 2 O 3 )] is preferably 0.12 or less, and more preferably in the range of 0 to 0.04.
- the above optical glass contains one or more alkali metal oxides selected from the group consisting of Li 2 O, Na 2 O and K 2 O as essential components.
- alkali metal oxides selected from the group consisting of Li 2 O, Na 2 O and K 2 O as essential components.
- the mass ratio of the total content of P 2 O 5 , B 2 O 3 and SiO 2 to the total content of Li 2 O, Na 2 O and K 2 O [(P 2 O 5 + B 2 O 3 + SiO 2 ) / (Na 2 O + K 2 O + Li 2 O)] is in the range of 1.39 to 1.80. When this mass ratio is less than 1.39, it becomes difficult to maintain devitrification resistance.
- the mass ratio [(P 2 O 5 + B 2 O 3 + SiO 2 ) / (Na 2 O + K 2 O + Li 2 O)] is preferably 1.40 or more, more preferably 1.42 or more, and still more preferably. It is 1.43 or more, more preferably 1.45 or more.
- the mass ratio [(P 2 O 5 + B 2 O 3 + SiO 2 ) / (Na 2 O + K 2 O + Li 2 O)] is preferably 1.67 or less. More preferably, it is 1.60 or less.
- Li 2 O content is preferably less than 0.3%. More preferably, it is 0.2% or less. From the viewpoint of further improving the devitrification resistance, it is preferable that Li 2 O is not contained (Li 2 O content is 0%). From the same viewpoint, it is preferable to suppress the Li 2 O content relative to the total content of alkali metal oxides. Specifically, the mass ratio [Li 2 O / (Na 2 O + K 2 O + Li 2 O)] is preferably less than 0.0115, and more preferably 0.003 or less.
- the other alkali metal oxides Na 2 O and K 2 O can be added to the above glass at least one, preferably at least Na 2 O, more preferably both.
- the mass ratio K 2 O / Na 2 O of the K 2 O content to the Na 2 O content is preferably 0.52 or less, and preferably 0.40 or less. More preferred.
- mass ratio K 2 O / Na 2 O can be, for example, 0.20 or more.
- Na 2 O content for example, can be 0% or more, preferably at least 8%, more preferably 11% or more.
- the K 2 O content can be, for example, 0% or more, preferably 2% or more, and more preferably 3% or more.
- the content of Na 2 O of the optical glass described above can be, for example, 16% or less, preferably 15% or less, and more preferably 14% or less.
- the K 2 O content is preferably 6% or less, more preferably 5% or less.
- the content of alkali metal oxides (when multiple types are included, the total content thereof) is preferably 10% or more, and preferably 30% or less from the viewpoint of maintaining devitrification resistance. 20% or less is more preferable. A preferred lower limit is 15%.
- TiO 2 is a component that can impart high refractive index and high dispersion characteristics to the glass when added in an appropriate amount, and is introduced as an essential component in the optical glass described above.
- the content thereof is Nb 2 O 5 , WO 3 , which is a component that can provide other high refractive index / high dispersion characteristics.
- TiO 2 content mass ratio of TiO 2 , Nb 2 O 5 , WO 3 , Bi 2 O 3 , and Ta 2 O 5 total content is set to an amount in the range of 0.059 to 0.180.
- this mass ratio is less than 0.059, it is difficult to obtain the above-described high refractive index / high dispersion characteristics. From the viewpoint of suppressing coloring, the upper limit is set to 0.180.
- the lower limit is preferably 0.10 or more, and more preferably 0.12 or more.
- the upper limit is preferably 0.178 or less, more preferably 0.170 or less, and further preferably 0.135 or less.
- the TiO 2 content is more preferably 6% or more. Further, from the viewpoint of maintaining the solubility of the glass and suppressing coloring, it is preferably 11% or less, and more preferably 9% or less.
- the total content of P 2 O 5 , B 2 O 3 and SiO 2 is changed to TiO 2 and Nb 2 which are high refractive index and high dispersion property imparting components.
- Mass ratio [(P 2 O 5 + B 2 O 3 + SiO 2 ) / (TiO 2 + Nb 2 O 5 + Bi 2 O 3 ) with respect to the total content of O 5 , WO 3 , Bi 2 O 3 and Ta 2 O 5 + Ta 2 O 5 )] is preferably 0.49 or more, more preferably 0.51 or more, and further preferably 0.52 or more.
- the mass ratio [(P 2 O 5 + B 2 O 3 ) / (TiO 2 + Nb 2 O 5 + Bi 2 O 3 + Ta 2 O 5 )] is set to 0. It is preferable to set it to 58 or less.
- the total content of TiO 2 , Nb 2 O 5 , WO 3 , Bi 2 O 3 , and Ta 2 O 5 is preferably more than 47% and 50% or more from the viewpoint of increasing the refractive index. More preferably. From the viewpoint of glass stability, the total content of TiO 2 , Nb 2 O 5 , WO 3 , Bi 2 O 3 , and Ta 2 O 5 is preferably 60% or less, and 55% or less. More preferably.
- Nb 2 O 5 is a component useful for obtaining a high refractive index and a high dispersion characteristic, and is also a component having an effect of improving durability. From the viewpoint of maintaining devitrification resistance and suppressing coloration, the Nb 2 O 5 content is preferably 47% or less. On the other hand, from the viewpoint of maintaining high refractive index and high dispersion characteristics, the Nb 2 O 5 content is preferably 19% or more, more preferably 40% or more, and more preferably 43% or more. preferable.
- WO 3 and Bi 2 O 3 are components that can be added to obtain high refractive index and high dispersion characteristics.
- the content of WO 3 and the content of Bi 2 O 3 in the optical glass described above can each be 15% or less.
- the WO 3 content and the Bi 2 O 3 content are each preferably 12% or less, preferably 6% or less, and may be 0%.
- the upper limit of WO 3 is preferably less than 13%, more preferably less than 3%, and still more preferably 2% or less.
- Ta 2 O 5 is an optional component that can be added to adjust the refractive index.
- the content can be, for example, 0 to 2%.
- the upper limit of Ta 2 O 5 content is less than 2%.
- the optical glass described above may contain one or more of the alkaline earth metal oxides MgO, CaO, SrO and BaO.
- the total content of MgO, CaO, SrO and BaO can be, for example, in the range of 0 to 10%.
- Alkaline earth metal oxide is a component having an effect of increasing the glass stability, but since it may cause a decrease in refractive index and a decrease in dispersibility, the total content is preferably suppressed to 2% or less, It may be 0%.
- the preferable lower limit of MgO content is 0% or more, and a preferable upper limit is 5% or less.
- the preferable lower limit of the CaO content is 0% or more, and the preferable upper limit is less than 1%.
- the preferable lower limit value of the SrO content is 0% or more, and the preferable upper limit value is 5% or less.
- the preferable lower limit of the BaO content is 0% or more, and the preferable upper limit is less than 7%, more preferably 6% or less.
- ZnO and Al 2 O 3 can also be added to the above optical glass as an optional component for adjusting the refractive index.
- the ZnO content is preferably less than 5% and may be 0%.
- the Al 2 O 3 content is preferably less than 3%, more preferably 2% or less, and may be 0%.
- F can be added in an amount of 2% or less, preferably less than 2%, based on the oxide. From the viewpoint of obtaining homogeneous glass, it is preferable not to introduce F.
- Sb 2 O 3 may be added to the above-described optical glass in an amount in the range of 0 to 0.1%, for example, as an external addition amount.
- the external addition amount of Sb 2 O 3 is preferably in the range of 0 to 0.02% from the viewpoint of preventing coloring.
- the glass composition of the above optical glass has been described above. Next, the glass characteristics of the above optical glass will be described.
- the above optical glass is a high refractive index and high dispersion optical glass having a refractive index nd in the range of 1.78 to 1.83 and an Abbe number ⁇ d in the range of 20 to 25.
- the lower limit of the refractive index nd is preferably 1.790 or more, more preferably 1.800 or more, and the upper limit is preferably less than 1.820, more preferably 1.815 or less.
- the lower limit of the Abbe number ⁇ d is preferably 21 or more, more preferably 22 or more, and the upper limit is preferably 24 or less, more preferably 23 or less.
- the optical glass having the above refractive index nd and Abbe number ⁇ d is useful in an optical system.
- the above-mentioned optical glass is an optical glass having high refractive index and high dispersion characteristics that can exhibit excellent devitrification resistance.
- One of the indicators of devitrification resistance is the liquidus temperature.
- the optical glass described above can exhibit a liquidus temperature of 1050 ° C. or lower, for example, and can also exhibit a liquidus temperature of 1000 ° C. or lower.
- the minimum of the liquidus temperature of the above-mentioned optical glass is 900 degreeC or more, for example, it is not specifically limited. Since glass with a low liquidus temperature has high devitrification stability near the softening point, it is possible to prevent crystals from being precipitated in the glass during heating for reheat pressing or heating in precision press molding.
- the temperature at the time of flowing out molten glass can be made low.
- the temperature at the time of flowing out molten glass can be made low.
- by reducing the temperature at which the molten glass flows out it is possible to suppress the occurrence of striae due to volatilization and to reduce fluctuations in optical characteristics.
- by lowering the liquidus temperature it is possible to suppress erosion of the melting crucible glass. As a result, it is possible to avoid a substance such as platinum constituting the crucible from being mixed into the glass due to erosion and becoming a foreign substance, or being dissolved as an ion and causing coloring of the glass.
- the glass transition temperature is preferably 500 ° C. or higher from the viewpoint of glass stability. On the other hand, from the viewpoint of obtaining good press formability, the glass transition temperature is preferably low, for example, preferably 570 ° C. or lower.
- the above-described optical glass is a glass having a high refractive index and a high dispersion characteristic, and suitable for any of the direct press method, the reheat press method, and the precision press method.
- optical glass according to aspect 2 includes the above-described glasses 2-A and 2-B. The details will be described below. Unless specified otherwise, the following applies to both glasses 2-A and 2-B.
- P 2 O 5 is an essential component as a glass forming component in phosphate glass.
- Phosphate glass has the characteristics that it can melt glass at a relatively low temperature and has high transmittance in the visible region.
- the lower limit of the P 2 O 5 content is 20% or more, preferably 21% or more.
- an upper limit is 34% or less, Preferably it is 30% or less, More preferably, it is 24% or less.
- B 2 O 3 is a component having an action of improving devitrification resistance by adding an appropriate amount to the phosphate glass. Therefore, more than 0% is introduced into the above optical glass as an essential component.
- the B 2 O 3 content is preferably 2% or more, more preferably 6% or more. However, if an excessive amount is included, it is difficult to achieve a high refractive index and a high dispersion characteristic, so the content is made 10% or less. Preferably it is 9% or less, More preferably, it is 8% or less.
- B The 2 O 3 content of 0% including the case where B 2 O 3 is contained in a trace amount to about impurity level in the glass.
- the content of B 2 O 3 greater than 0% refers to the B 2 O 3 is contained in an amount exceeding about impurity levels. Specifically, it is 700 ppm (mass ratio) or more, or 1000 ppm (mass ratio) or more, for example.
- the mass ratio of the P 2 O 5 content to the B 2 O 3 content is more than 0 and less than 0.39.
- a more preferred lower limit is 0.15, and a more preferred lower limit is 0.25.
- a more preferred upper limit is 0.38.
- the total content of P 2 O 5 and B 2 O 3 and the total content of TiO 2 , Nb 2 O 5 , WO 3 , Bi 2 O 3 and Ta 2 O 5 is defined. Details thereof will be described later.
- SiO 2 is an optional component that may be contained in the optical glass described above. From the viewpoint of increasing the refractive index, the content is preferably 2% or less, preferably 1.2% or less, preferably 1.0% or less, even if not introduced ( (The SiO 2 content may be 0%). From the viewpoint of improving devitrification resistance, in the glass B, the mass ratio of the SiO 2 content to the total content of SiO 2 , P 2 O 5 and B 2 O 3 [SiO 2 / (SiO 2 + P 2 O 5 + B 2 O 3 )] is preferably less than 0.02 and preferably in the range of 0 to 0.01.
- the mass ratio of the SiO 2 content to the total content of SiO 2 , P 2 O 5 and B 2 O 3 [SiO 2 / (SiO 2 + P 2 O 5 + B 2 O 3 ) ] is preferably less than 0.02, more preferably in the range of 0 to 0.01.
- the optical glass described above can contain one or more alkali metal oxides.
- the alkali metal oxide includes Li 2 O, Na 2 O and K 2 O.
- the content is less than 0.3%. More preferably, it is 0.2% or less. From the viewpoint of further improving the devitrification resistance, it is preferable that Li 2 O is not contained (Li 2 O content is 0%).
- the other alkali metal oxides Na 2 O and K 2 O can be added to the above glass at least one, preferably at least Na 2 O, more preferably both.
- the mass ratio K 2 O / Na 2 O of the K 2 O content to the Na 2 O content is preferably 0.52 or less, and preferably 0.40 or less. More preferred.
- mass ratio K 2 O / Na 2 O can be, for example, 0.20 or more.
- Na 2 O content for example, can be 0% or more, preferably at least 8%, more preferably 11% or more.
- the K 2 O content can be, for example, 0% or more, preferably 2% or more, and more preferably 3% or more.
- the content of Na 2 O of the optical glass described above can be, for example, 16% or less, preferably 15% or less, and more preferably 14% or less.
- the K 2 O content is preferably 6% or less, more preferably 5% or less.
- the content of alkali metal oxides (when multiple types are included, the total content thereof) is preferably 10% or more, and preferably 30% or less from the viewpoint of maintaining devitrification resistance. 20% or less is more preferable. A preferred lower limit is 15%.
- TiO 2 is a component that can impart high refractive index and high dispersion characteristics to the glass when added in an appropriate amount, and is introduced as an essential component in the optical glass described above.
- the content thereof is Nb 2 O 5 , WO 3 , which is a component that can provide other high refractive index / high dispersion characteristics.
- TiO 2 content mass ratio of TiO 2 , Nb 2 O 5 , WO 3 , Bi 2 O 3 , and Ta 2 O 5 total content is set to an amount in the range of 0.059 to 0.96.
- this mass ratio is less than 0.059, it is difficult to obtain the above-described high refractive index / high dispersion characteristics, and when it exceeds 0.96, it is difficult to maintain devitrification resistance.
- the mass ratio [TiO 2 / (TiO 2 + Nb 2 O 5 + WO 3 + Bi 2 O 3 + Ta 2 O 5 )] is preferably 0.10 or more, more preferably 0.12 or more, and It is preferably 50 or less, and more preferably 0.20 or less. From the viewpoint of high refractive index and high dispersion characteristics, the TiO 2 content is more preferably 6% or more. Further, from the viewpoint of maintaining the solubility of the glass and suppressing coloring, it is preferably 11% or less, and more preferably 9% or less.
- the total content of P 2 O 5 and B 2 O 3 or the total content of P 2 O 5 , B 2 O 3 and SiO 2 is increased. It is specified with respect to the total content of TiO 2 , Nb 2 O 5 , WO 3 , Bi 2 O 3 and Ta 2 O 5 which are components for imparting refractive index and high dispersion characteristics. More specifically, in the glass A, the mass ratio [(P 2 O 5 + B 2 O 3 ) / (TiO 2 + Nb 2 O 5 + WO 3 + Bi 2 O 3 + Ta 2 O 5 )] is more than 0.53.
- the mass ratio [(P 2 O 5 + B 2 O 3 + SiO 2 ) / (TiO 2 + Nb 2 O 5 + WO 3 + Bi 2 O 3 + Ta 2 O 5 )] is set to exceed 0.53.
- the mass ratio [(P 2 O 5 + B 2 O 3 ) / (TiO 2 + Nb 2 O 5 + WO 3 + Bi 2 O 3 + Ta 2 O 5 )] is It is preferable to set it as 0.75 or less, and it is more preferable to set it as 0.58 or less.
- the mass ratio [(P 2 O 5 + B 2 O 3 + SiO 2 ) / (TiO 2 + Nb 2 O 5 + WO 3 + Bi 2 O 3 + Ta 2 O 5 )] should be 0.75 or less. Preferably, it is 0.58 or less.
- the total content of TiO 2 , Nb 2 O 5 , WO 3 , Bi 2 O 3 , and Ta 2 O 5 is preferably more than 47% and 50% or more from the viewpoint of increasing the refractive index. More preferably. From the viewpoint of glass stability, the total content of TiO 2 , Nb 2 O 5 , WO 3 , Bi 2 O 3 , and Ta 2 O 5 is preferably 60% or less, and 55% or less. More preferably.
- Nb 2 O 5 is a component useful for obtaining a high refractive index and a high dispersion characteristic, and is also a component having an effect of improving durability. From the viewpoint of maintaining devitrification resistance and suppressing coloration, the Nb 2 O 5 content is preferably 47% or less. On the other hand, from the viewpoint of maintaining high refractive index and high dispersion characteristics, the Nb 2 O 5 content is preferably 19% or more, more preferably 40% or more, and more preferably 43% or more. preferable.
- WO 3 and Bi 2 O 3 are components that can be added to obtain high refractive index and high dispersion characteristics.
- the content of WO 3 and the content of Bi 2 O 3 in the optical glass described above can each be 15% or less. Can be introduced.
- the WO 3 content and the Bi 2 O 3 content are each preferably 12% or less, preferably 6% or less, and may be 0%.
- the upper limit of WO 3 is preferably less than 3%, more preferably 2% or less.
- Ta 2 O 5 is an optional component that can be added to adjust the refractive index.
- the content can be, for example, 0 to 2%.
- the optical glass described above may contain one or more of the alkaline earth metal oxides MgO, CaO, SrO and BaO.
- the total content of MgO, CaO, SrO and BaO can be, for example, in the range of 0 to 10%.
- Alkaline earth metal oxide is a component having an effect of increasing the glass stability, but since it may cause a decrease in refractive index and a decrease in dispersibility, the total content is preferably suppressed to 2% or less, It may be 0%.
- the preferable lower limit of MgO content is 0% or more, and a preferable upper limit is 5% or less.
- the preferable lower limit of the CaO content is 0% or more, and the preferable upper limit is less than 1%.
- the preferable lower limit value of the SrO content is 0% or more, and the preferable upper limit value is 5% or less.
- the preferable lower limit of the BaO content is 0% or more, and the preferable upper limit is less than 7%, more preferably 6% or less.
- ZnO and Al 2 O 3 can also be added to the above optical glass as an optional component for adjusting the refractive index.
- the ZnO content is preferably less than 5% and may be 0%.
- the Al 2 O 3 content is preferably 2% or less, and may be 0%.
- F can be added in an amount of 2% or less based on the oxide. From the viewpoint of obtaining homogeneous glass, it is preferable not to introduce F. Further, SnO 2 and Sb 2 O 3 may be added to the above-mentioned optical glass in amounts of, for example, 0 to 1%, respectively, as external addition amounts.
- the glass composition of the above optical glass has been described above. Next, the glass characteristics of the above optical glass will be described.
- the above optical glass is a high refractive index and high dispersion optical glass having a refractive index nd in the range of 1.78 to 1.83 and an Abbe number ⁇ d in the range of 20 to 25.
- the lower limit of the refractive index nd is preferably 1.790 or more, more preferably 1.800 or more, and the upper limit is preferably less than 1.820, more preferably 1.815 or less.
- the lower limit of the Abbe number ⁇ d is preferably 21 or more, more preferably 22 or more, and the upper limit is preferably 24 or less, more preferably 23 or less.
- the optical glass having the above refractive index nd and Abbe number ⁇ d is useful in an optical system.
- the above-mentioned optical glass is an optical glass having high refractive index and high dispersion characteristics that can exhibit excellent devitrification resistance.
- One of the indicators of devitrification resistance is the liquidus temperature.
- the optical glass described above can exhibit a liquidus temperature of 1050 ° C. or lower, for example, and can also exhibit a liquidus temperature of 1000 ° C. or lower.
- the minimum of the liquidus temperature of the above-mentioned optical glass is 900 degreeC or more, for example, it is not specifically limited. Since glass with a low liquidus temperature has high devitrification stability near the softening point, it is possible to prevent crystals from being precipitated in the glass during heating for reheat pressing or heating in precision press molding.
- the temperature at the time of flowing out molten glass can be made low.
- the temperature at the time of flowing out molten glass can be made low.
- by reducing the temperature at which the molten glass flows out it is possible to suppress the occurrence of striae due to volatilization and to reduce fluctuations in optical characteristics.
- by lowering the liquidus temperature it is possible to suppress erosion of the melting crucible glass. As a result, it is possible to avoid a substance such as platinum constituting the crucible from being mixed into the glass due to erosion and becoming a foreign substance, or being dissolved as an ion and causing coloring of the glass.
- the glass transition temperature is preferably 500 ° C. or higher from the viewpoint of glass stability. On the other hand, from the viewpoint of obtaining good press formability, the glass transition temperature is preferably low, for example, preferably 570 ° C. or lower.
- the above-described optical glass is a glass having a high refractive index and a high dispersion characteristic, and suitable for any of the direct press method, the reheat press method, and the precision press method.
- the optical glass according to Aspect 3 has an oxide-based glass composition in which P 2 O 5 is 24 to 34% by mass, B 2 O 3 is more than 0% by mass and 4% by mass, Na 2 O, K 2 O, and It contains 12 to 20% by mass of Li 2 O, 15 to 30% by mass of Nb 2 O 5 , 8 to 15% by mass of TiO 2 , and 4 to 25% by mass of Bi 2 O 3 , and the mass ratio (TiO 2 / Nb 2 O 5 ) is in the range of 0.36 to 1.00, the mass ratio (Bi 2 O 3 / Nb 2 O 5 ) is in the range of 0.16 to 1.67, and the refractive index nd is 1.
- P 2 O 5 is an essential component as a glass forming component in phosphate glass.
- Phosphate glass has the characteristics that it can melt glass at a relatively low temperature and has high transmittance in the visible region.
- P 2 O 5 is a component located on the high dispersion side as compared with SiO 2 and B 2 O 3 which are the same glass forming components, and the content thereof is obtained in order to obtain the high dispersion characteristic indicating the above Abbe number ⁇ d.
- it is 27% or more, more preferably 28% or more.
- the content is set to 34% or less.
- it is 31% or less, More preferably, it is 30% or less.
- SiO 2 is an optional component that can be added to the above-described optical glass, and has an effect of increasing devitrification resistance. From the viewpoint of obtaining a high refractive index characteristic, if the above-mentioned optical glass includes SiO 2, is preferably SiO 2 content is 1.2% or less. More preferably, it is 1.0% or less, more preferably less than 0.5%, still more preferably 0.4% or less, and it may not be introduced (even if the SiO 2 content is 0%).
- B 2 O 3 is a component having an action of improving devitrification resistance by adding an appropriate amount to the phosphate glass. Therefore, more than 0% is introduced into the above optical glass as an essential component.
- the B 2 O 3 content is preferably 0.4% or more, more preferably 0.7% or more. However, if an excessive amount is included, it is difficult to realize a high refractive index and a high dispersion characteristic, so the content is made 4% or less. Preferably it is 3% or less, More preferably, it is 1.5% or less.
- the B 2 O 3 content of 0% includes a case where B 2 O 3 is contained in a glass in a trace amount to an impurity level.
- the content of B 2 O 3 is greater than 0% refers to the B 2 O 3 is contained in an amount exceeding about impurity levels. Specifically, it is 700 ppm (mass ratio) or more, or 1000 ppm (mass ratio) or more, for example.
- the glass characteristics that the glass suitable for precision press molding desirably has include a low glass transition temperature. This is because it is necessary to increase the press molding temperature in order to press-mold a glass having a high glass transition temperature Tg. However, if the precision press molding temperature is increased, it is provided on the molding die itself or the molding surface of the molding die. It is because the release film which exists is damaged. In the precision press molding method, an optical functional surface is formed by transferring a molding die molding surface without machining such as grinding and polishing. Therefore, when the molding die or the release film is damaged and the molding surface becomes rough, the rough surface shape is transferred to the optical element, and an optical functional surface having high surface smoothness cannot be obtained.
- the above-described optical glass preferably has a relatively low glass transition temperature, specifically, a glass transition temperature of 520 ° C. or lower.
- the glass transition temperature is more preferably 510 ° C. or lower, further preferably 500 ° C. or lower, and further preferably 490 ° C. or lower.
- the glass transition temperature is preferably higher than 460 ° C, more preferably 465 ° C or higher, and further preferably 470 ° C or higher.
- the mass ratio (B 2 O 3 / P 2 O 5 ) between the P 2 O 5 content and the B 2 O 3 content is set to 0 It is preferable to be over 0.1. More preferably, it is more than 0 and 0.083 or less.
- the total content of the alkali metal oxides Na 2 O, K 2 O, and Li 2 O in the above optical glass is 12% or more.
- the total content is 20% or less. Preferably it is 17% or less, More preferably, it is 16% or less.
- Li 2 O may include one or two or more selected from the group consisting of Na 2 O and K 2 O.
- Introducing at least Na 2 O as the alkali metal oxide is advantageous for obtaining an optical glass exhibiting a low glass transition temperature.
- the Na 2 O content in the optical glass is preferably 2% or more, more preferably 4% or more, and further preferably 5% or more.
- the Na 2 O content is preferably 12% or less, more preferably 9% or less, and even more preferably 8% or less.
- K 2 O and Li 2 O are all components that can be added to lower the glass transition temperature.
- the K 2 O content of the optical glass described above can be, for example, 2% or more, and is preferably 4% or more.
- the Li 2 O content can be, for example, 1% or more, and is preferably 2% or more. Further, from the viewpoint of devitrification resistance, the K 2 O content can be, for example, 8% or less, and preferably 7% or less.
- the Li 2 O content can be, for example, 5% or less, and is preferably 4% or less.
- Nb 2 O 5 is an indispensable component for obtaining a high refractive index and a high dispersion characteristic, and is also a component having an effect of improving durability. If Nb 2 O 5 is less than 15%, it is difficult to obtain the desired high refractive index and high dispersion characteristics, and if it exceeds 30%, the devitrification resistance of the glass is lowered. Therefore, in the above optical glass, the Nb 2 O 5 content is in the range of 15 to 30%. From the viewpoint of realizing more preferable high refractive index and high dispersion characteristics, the Nb 2 O 5 content is preferably 25% or less, more preferably 22% or less, and even more preferably 20% or less. . Further, from the viewpoint of devitrification resistance, the Nb 2 O 5 content is preferably 16% or more, and more preferably 18% or more.
- TiO 2 is a component that can impart high refractive index and high dispersion characteristics to the glass when added in an appropriate amount, and 8% or more is introduced into the optical glass.
- the TiO 2 content is preferably 9% or more, more preferably 10% or more. However, when the content exceeds 15%, the devitrification resistance decreases, so the TiO 2 content in the optical glass is set to 15% or less. Preferably it is 13% or less, More preferably, it is 12% or less.
- Bi 2 O 3 is a useful component for lowering the glass transition temperature and improving precision press molding. Therefore, 4% or more of Bi 2 O 3 is introduced into the above optical glass.
- the Bi 2 O 3 content is preferably 6% or more, more preferably 10% or more.
- the Bi 2 O 3 content in the optical glass is set to 25% or less. Preferably it is 20% or less, More preferably, it is 15% or less.
- Nb 2 O 5 , TiO 2 , and Bi 2 O 3 are as described above. Further, in the above optical glass, the mass ratio (TiO 2 / Nb 2 O 5 ) is in the range of 0.36 to 1.00, and the mass ratio (Bi 2 O 3 / Nb 2 O 5 ) is 0.16 to The range is 1.67.
- the ratio of Nb 2 O 5 and TiO 2 which are useful components for imparting high refractive index and high dispersion characteristics, and Bi 2 O 3 which is a component useful for improving precision press moldability are within the above range.
- a phosphoric acid optical glass having a high refractive index and a high dispersion characteristic of a refractive index nd of 1.78 or more and less than 1.83 and an Abbe number ⁇ d in the range of 20 to 25 and suitable for precision press molding can be obtained.
- the lower limit of the mass ratio (TiO 2 / Nb 2 O 5 ) is preferably 0.40 or more, and preferably 0.50 or more. Is more preferably 0.55 or more.
- the upper limit is preferably 0.80 or less, more preferably 0.70 or less, and even more preferably 0.60 or less.
- the lower limit of the mass ratio (Bi 2 O 3 / Nb 2 O 5 ) is preferably 0.20 or more, more preferably 0.40 or more, and 0.50 or more. More preferably, it is more preferably 0.60 or more.
- the upper limit is preferably 0.87 or less, more preferably 0.80 or less, and even more preferably 0.70 or less.
- the optical glass described above may contain one or more of the alkaline earth metal oxides MgO, CaO, SrO and BaO.
- Alkaline earth metal oxides are components that have the effect of enhancing glass stability, but may cause a decrease in refractive index and a decrease in dispersibility. Therefore, the total content of the alkaline earth metal oxides MgO, CaO, SrO and BaO is preferably suppressed to 2% or less, and may be 0%.
- the total content of the alkali metal oxide and the alkaline earth metal oxide (Li 2 O + Na 2 O + K 2 O + MgO + CaO + SrO + BaO) may be in the range of 12 to 17% from the viewpoint of realizing high refractive index and high dispersion characteristics.
- the upper limit value is more preferably 17% or less, and still more preferably 16% or less.
- the preferable lower limit of MgO content is 0% or more, and a preferable upper limit is 2% or less.
- the preferable lower limit of the CaO content is 0% or more, and the preferable upper limit is 2% or less, more preferably less than 1%.
- the preferable lower limit value of the SrO content is 0% or more, and the preferable upper limit value is 2% or less.
- the preferable lower limit of the BaO content is 0% or more, and the preferable upper limit is 2% or less.
- WO 3 is an optional component that can be added to the glass described above, and has the effect of contributing to the low Tg of the glass and improving the precision press formability. From the viewpoint of forming an optical glass suitable for precision press molding, it is preferable that 3% or more of WO 3 is contained in the optical glass. More preferably, it is 6% or more, More preferably, it is 10% or more. On the other hand, from the viewpoint of devitrification resistance, the content of WO 3 is preferably 23% or less, more preferably 20% or less, and even more preferably less than 13%.
- the ratio of the WO 3 content to the Nb 2 O 5 content is set so that the mass ratio (WO 3 / Nb 2 O 5 ) is in the range of 0.12 to 0.92. It is preferable to adjust. From the viewpoint of achieving both high refractive index / high dispersion characteristics and low Tg, the lower limit of the mass ratio (WO 3 / Nb 2 O 5 ) is more preferably 0.20, still more preferably 0.50, and more More preferably, it is 0.55. The upper limit value is more preferably 0.80, and still more preferably 0.70.
- ZnO, Al 2 O 3 , and Ta 2 O 5 can also be added to the above optical glass as optional components for adjusting the refractive index.
- the contents of ZnO, Al 2 O 3 and Ta 2 O 5 can be, for example, in the range of 0 to 5%, preferably in the range of 0 to 3%.
- La 2 O 3 , Y 2 O 3 , Gd 2 O 3 , Cs 2 O, ZrO 2 , PbO, etc. each in an amount in the range of 0 to 1%, for example, does not impair the purpose of the present invention. You may add in the range.
- SnO 2 and Sb 2 O 3 may be added to the above-mentioned optical glass in amounts of, for example, 0 to 1%, respectively, as external addition amounts.
- the glass composition of the above optical glass has been described above. Next, the glass characteristics of the above optical glass will be described.
- the above-mentioned optical glass is a high refractive index and high dispersion optical glass having a refractive index nd of 1.78 or more and less than 1.83 and an Abbe number ⁇ d in the range of 20-25.
- the lower limit of the refractive index nd is preferably 1.790 or more, more preferably 1.795 or more, and further preferably 1.800 or more.
- the upper limit is preferably 1.820 or less, more preferably 1.815 or less, and still more preferably 1.810 or less.
- the lower limit of the Abbe number ⁇ d is preferably 21.0 or more, and more preferably 22.0 or more.
- the upper limit is preferably 24.0 or less, and more preferably 23.5 or less.
- the optical glass having the above refractive index nd and Abbe number ⁇ d is useful in an optical system.
- a preferred embodiment of the above-described optical glass includes a glass having a refractive index and an Abbe number ⁇ d satisfying the following formula (1).
- nd ⁇ 15 / ⁇ d + 1.18 (1)
- the glass transition temperature of the optical glass described above is as described above.
- compositions effective for lowering Tg include the following compositions. Although the Tg can be lowered simply by increasing the content of alkali metal oxide or alkaline earth metal oxide, the weather resistance may deteriorate as a result. On the other hand, the following composition is mentioned as a preferable composition which can aim at low Tg suitable for precision press molding, maintaining a weather resistance.
- the total content of Li 2 O, Na 2 O, K 2 O, MgO, CaO, SrO and BaO is in the range of 12 to 17%, and the mass ratio (B 2 O 3 / P 2 O 5 ) In the range of more than 0 and 0.1 or less.
- the total content of Li 2 O, Na 2 O, K 2 O, MgO, CaO, SrO and BaO is in the range of 12 to 17%, and the mass ratio (B 2 O 3 / P 2 O 5 ) Is preferably a composition in the range of more than 0 and 0.083 or less.
- the total content of Li 2 O, Na 2 O, K 2 O, MgO, CaO, SrO and BaO is in the range of 12 to 17%, and the mass ratio (Bi 2 O 3 / Nb 2 O 5 ) In the range of 0.16 to 1.67.
- the total content of Li 2 O, Na 2 O, K 2 O, MgO, CaO, SrO and BaO is in the range of 12 to 17%, and the mass ratio (Bi 2 O 3 / Nb 2 O 5 ) In the range of 0.16 to 0.87.
- the total content of Li 2 O, Na 2 O, K 2 O, MgO, CaO, SrO and BaO is in the range of 12 to 17%, and the mass ratio (WO 3 / Nb 2 O 5 ) is 0 Composition in the range of 12 to 0.92.
- the mass ratio (TiO 2 / Nb 2 O 5 ) is in the range of 0.36 to 1.00, and the total content of Li 2 O, Na 2 O, K 2 O, MgO, CaO, SrO and BaO A composition whose amount ranges from 12 to 17%.
- the mass ratio (TiO 2 / Nb 2 O 5 ) is in the range of 0.40 to 0.80, and the total content of Li 2 O, Na 2 O, K 2 O, MgO, CaO, SrO and BaO
- a preferred range of amounts is a composition in the range of 12-17%.
- the optical glass desirably has from the point of precision press moldability
- a low liquidus temperature can also be mentioned.
- Glass having a low liquidus temperature has high devitrification stability in the vicinity of the softening point. Therefore, the preform is heated to be softened and precision press-molded to obtain an optical element having high transparency without devitrification. Because it can. From this point, it is preferable that the above-mentioned optical glass has a liquidus temperature of 1000 ° C. or lower.
- the liquidus temperature is more preferably 970 ° C. or less, and still more preferably 960 ° C. or less. Further, from the viewpoint of glass stability, the liquidus temperature is preferably 850 ° C. or higher, and more preferably 880 ° C. or higher.
- the above-described optical glass is an optical glass having high refractive index and high dispersion characteristics and suitable for precision press molding.
- the raw materials such as oxide, carbonate, sulfate, nitrate, and hydroxide are weighed, prepared, and mixed so that the desired glass composition can be obtained.
- a mixed batch can be obtained by heating, melting, defoaming and stirring in a melting container to form a molten glass that is homogeneous and free of bubbles, and is molded. Specifically, it can be made using a known melting method.
- Optical element blanks, glass materials for press molding, and methods for producing them are: Optical element blank made of optical glass according to aspect 1 or aspect 2; A glass material for press molding comprising the optical glass according to aspect 1 or aspect 2; A method for producing a glass material for press molding, comprising a step of forming the optical glass according to aspect 1 or 2 into a glass material for press molding; and In the state where the glass material for press molding is softened by heating, a method for producing an optical element blank including a step of producing an optical element blank by press molding using a press mold, About.
- the optical element blank is an optical element base material that approximates the shape of the target optical element and adds a grinding and polishing margin to the shape of the optical element.
- the optical element is finished by grinding and polishing the surface of the optical element blank.
- An optical element blank can be produced by press molding using a press mold in a state where the glass material for press molding made of the optical glass is softened by heating. Since the optical glass described above can exhibit excellent devitrification resistance, crystals can be prevented from being precipitated in the glass by heating during press molding.
- Both heating and press molding of the glass material for press molding can be performed in the air.
- a powder release agent such as boron nitride
- heating and press molding it is possible to reliably prevent the glass and the mold from being fused, and the molding surface of the press mold
- the glass can be smoothly extended along.
- a uniform optical element blank can be obtained by annealing after press molding to reduce strain inside the glass.
- a glass material for press molding also called a preform
- machining such as cutting, grinding and polishing
- a cutting method a groove is formed in a portion of the surface of the glass plate to be cut by a method called scribing, and a local pressure is applied to the groove portion from the back surface of the surface on which the groove is formed.
- a method of breaking a plate and a method of cutting a glass plate with a cutting blade.
- barrel polishing etc. are mentioned as a grinding
- An optical element comprising the optical glass according to aspect 1 or 2;
- a method for producing an optical element comprising a step of producing an optical element by grinding and / or polishing the above-described optical element blank;
- Method B a method for producing an optical element including a step of producing an optical element by press molding using a press mold, About.
- Method A known methods may be applied to grinding and polishing, and an optical element having high internal quality and high surface quality can be obtained by sufficiently washing and drying the surface of the optical element after processing.
- Method A is suitable as a method for manufacturing optical elements such as various spherical lenses and prisms.
- Precision press molding in Method B is also called mold optics molding, and is a method of forming the optical functional surface of the optical element by transferring the molding surface of the press mold.
- a surface that transmits, refracts, diffracts, or reflects light rays of the optical element is referred to as an optical functional surface.
- a lens surface such as an aspherical surface of an aspherical lens or a spherical surface of a spherical lens corresponds to an optical functional surface.
- the precision press molding method is a method of forming an optical functional surface by press molding by precisely transferring a molding surface of a press mold to glass.
- the precision press molding method is suitable for manufacturing optical elements such as lenses, lens arrays, diffraction gratings, and prisms, and is particularly suitable as a method for manufacturing an aspheric lens with high productivity.
- the preform having a clean surface was reheated so that the viscosity of the glass constituting the preform was in the range of 10 5 to 10 11 Pa ⁇ s, and reheated.
- the preform is press-molded with a mold having an upper mold and a lower mold.
- a mold release film may be provided on the molding surface of the mold as necessary.
- the press molding is preferably performed in an atmosphere of nitrogen gas or inert gas in order to prevent oxidation of the molding surface of the mold.
- the press-molded product is taken out from the mold and gradually cooled as necessary.
- the molded product is an optical element such as a lens, an optical thin film may be coated on the surface as necessary.
- Optical elements such as arrays, diffraction gratings, and prisms can be manufactured.
- Aspect 3 also relates to a precision press-molding preform made of the optical glass described above.
- a precision press-molding preform (hereinafter also referred to as a preform) means a glass lump to be subjected to precision press molding, and is a glass molded body corresponding to the mass of a precision press-molded product.
- the precision press molding is as described above.
- the preform may be manufactured through cold processing such as grinding and polishing, or by hot processing (also referred to as hot forming) in which a molded product is obtained from molten glass without undergoing cold processing such as grinding and polishing. It may be produced.
- hot processing also referred to as hot forming
- Glass properties suitable for this hot working include low Tg and low liquidus temperature. Since the above-mentioned optical glass can have these glass characteristics, it is also suitable for obtaining a preform by hot working.
- a uniform molten glass is produced by melting, clarifying, and stirring the glass raw material from which the above optical glass can be obtained. Thereafter, the molten glass is allowed to flow out from a platinum or platinum alloy pipe to produce a glass lump from a predetermined amount of molten glass, and a hot-formed product is formed using the glass lump.
- the molten glass is continuously discharged from the outlet of the above-mentioned pipe, and the tip portion of the glass that has flowed out of the outlet is separated to obtain a predetermined amount of glass lump.
- the obtained glass lump is formed into a preform shape while the glass is in a temperature range where plastic deformation is possible.
- Examples of the method for separating the tip portion of the outflow glass include a dropping method and a descending cutting method.
- a dropping method By using the optical glass described above, it is possible to separate the tip portion of the glass flowing out from the pipe outlet without devitrifying the glass.
- a preform with a constant weight By keeping the outflow speed and outflow temperature constant, and keeping the dripping condition or descent condition constant, a preform with a constant weight can be manufactured with high reproducibility and high accuracy.
- a preform having a mass of, for example, 1 to 5000 mg can be manufactured with high mass accuracy.
- the separated glass tip is received by a molding die in which gas is ejected from a concave molding surface, and is molded into a preform such as a sphere or an ellipsoid by levitation and rotation by the wind pressure of the gas. .
- a molding method is called a floating molding method.
- a method of obtaining a preform by press-molding a molten glass lump with a lower mold and an upper mold is also known, and can be used for the above-described hot forming.
- the hot-formed product thus manufactured may be provided with a known release film on the surface as necessary.
- An optical element comprising the optical glass according to aspect 3; and An optical element manufacturing method comprising a step of producing an optical element by precision press molding using a press mold in a state where the above-described precision press molding preform is softened by heating, About.
- the precision press molding method is as described above. Since the above-mentioned preform can have a low Tg, which is a glass characteristic suitable for precision press molding, the glass can be pressed at a relatively low temperature. Therefore, since the burden on the molding surface of the press mold is reduced, the life of the molding die can be extended and the molding surface of the molding die can be prevented from being damaged and roughened.
- Optical elements such as lens arrays, diffraction gratings, and prisms can be manufactured with high accuracy and high productivity.
- the molten glass is poured into a 40 ⁇ 70 ⁇ 15 mm carbon mold, allowed to cool to the glass transition temperature, immediately put into an annealing furnace, annealed for about 1 hour in the glass transition temperature range, and room temperature in the furnace.
- Each optical glass was produced.
- the refractive index, Abbe number, glass transition temperature, and liquidus temperature of each optical glass were measured by the following methods.
- a 1 cm square glass sample was heated in the first test furnace set to the glass transition temperature Tg of the glass for 10 minutes, and further heated to the second test furnace set to Tg plus 10 ° C. of the glass for 10 minutes.
- the presence or absence of crystals or cloudiness was confirmed with an optical microscope (observation magnification: 10 to 100 times).
- observation magnification 10 to 100 times.
- Examples 1-1 to 1-28 are examples according to Aspect 1
- Comparative Examples 1-1 and 1-2 are comparative examples with respect to Aspect 1.
- Examples 2-1 to 2-28 are examples according to aspect 2
- comparative examples 2-1 to 2-3 are comparative examples for aspect 2.
- the optical glass having the composition of Examples 2, 3, and 6 described in JP-A-6-345481 having a glass composition different from that of the optical glass according to one embodiment of the present invention is obtained.
- Optical glass was produced in the same manner as in the example. About the produced optical glass, when the above-mentioned devitrification evaluation was performed, all the evaluation results were "x".
- the optical glass having the composition of Example 10 described in JP-A No. 5-270853 having a glass composition different from that of the optical glass according to one embodiment of the present invention is obtained.
- Optical glass was produced by the same method.
- nd was 1.762202 and ⁇ d was 25.24, which did not have the optical characteristics that the above optical glass satisfies. It was confirmed.
- the same evaluation was performed on Example 4 described in Japanese Patent Laid-Open No. 6-345481 which has a glass composition different from that of the optical glass according to one embodiment of the present invention.
- nd was 1.72914 and ⁇ d was 26.22. In other words, it was confirmed that the above optical glass does not have optical characteristics.
- Examples 3-1 to 3-19 are examples according to Aspect 3.
- a high-quality and homogenized molten glass from which each optical glass of Examples according to Embodiments 1 to 3 was obtained was continuously discharged from a platinum alloy pipe.
- the molten glass flowing out was dropped from the pipe outlet, received one after another by a plurality of preform molding dies, and a plurality of spherical preforms were molded by a floating molding method.
- the temperature of the glass at the time of outflow was made several degree C higher than the liquidus temperature.
- the preform obtained from the optical glass of the example was transparent and homogeneous with no crystal observable with a microscope. None of these preforms was devitrified, and a material with high mass accuracy was obtained.
- a preform was produced by using a descending cutting method instead of the dropping method. Similarly, devitrification was not observed in the preform obtained by the descending cutting method, and a preform with high mass accuracy was obtained. Moreover, the trace at the time of isolation
- Examples relating to optical elements The surface of the above-mentioned preform is coated as necessary, and introduced into a press mold including an upper and lower mold made of SiC and a body mold provided with a carbon-based release film on the molding surface, and nitrogen. A mold and a preform are heated together in an atmosphere to soften the preform, precision press-molded, and aspherical convex meniscus lens, aspherical concave meniscus lens, aspherical biconvex lens, aspherical both Various lenses of concave lenses were prepared. In addition, each condition of precision press molding was adjusted in the above-mentioned range.
- the surface of the lens thus obtained may be coated with an antireflection film.
- the same preform as the above-mentioned preform is heated and softened, introduced into a separately preheated press mold, precision press-molded, and aspherical convex meniscus lens, aspherical concave meniscus lens, Various lenses such as a spherical biconvex lens and an aspherical biconcave lens were prepared.
- each condition of precision press molding was adjusted in the above-mentioned range.
- the surface of the lens thus obtained may be coated with an antireflection film.
- Examples relating to optical element blank and optical element Prepare clarified and homogenized molten glass from which the glass of the example according to the above-described aspect 1 and the example according to the aspect 2 can be obtained, and continuously from a platinum pipe at a constant flow rate. Then, the glass plate was poured into a mold having a side wall opened horizontally below the pipe, and formed into a glass plate having a certain width and thickness, and the molded glass plate was pulled out from the opening of the mold. The drawn glass plate was annealed in an annealing furnace to obtain a glass plate made of each of the above optical glasses with reduced distortion, no striae or foreign matter, and little coloration.
- these glass plates were cut vertically and horizontally to obtain a plurality of rectangular parallelepiped glass pieces having the same dimensions. Further, a plurality of glass pieces were barrel-polished to make a glass gob for press molding according to the weight of the target press-formed product.
- the molten glass flows out from the platinum nozzle at a constant flow rate, and a number of receiving molds are successively transferred to the lower part of the nozzle to receive a predetermined mass of molten glass ingot one after another.
- a glass gob may be formed into a spherical or rotating body shape, annealed and then barrel-polished to match the mass of the target press-formed product, and a glass gob for press forming may be used.
- a powder mold release agent for example, boron nitride powder, is applied to the entire surface of each glass gob, heated and softened with a heater, and then placed in a press mold having an upper mold and a lower mold.
- Each lens blank having a shape approximate to a lens obtained by adding pressure to the target lens shape by applying pressure and grinding and polishing was formed.
- each lens blank was annealed to reduce distortion.
- the cooled lens blank was ground and polished to finish the target lens.
- the series of steps was performed in the atmosphere.
- Each of the obtained lenses had excellent light transmittance.
- the lens may be coated with an optical multilayer film such as an antireflection film. With such a lens, a good imaging optical system can be configured.
- other optical elements such as a prism, can also be manufactured by appropriately setting the shape of the press mold and the volume of the glass gob.
- the P 2 O 5 content is 20 to 34% by mass
- the B 2 O 3 content is more than 0% by mass and 10% by mass or less
- the mass ratio (B 2 O 3 / P 2 O 5 ) is more than 0 and less than 0.39
- the mass ratio [TiO 2 / (TiO 2 + Nb 2 O 5 + WO 3 + Bi 2 O 3 + Ta 2 O 5 )] is 0.059 to 0.180.
- the range and mass ratio [(P 2 O 5 + B 2 O 3 + SiO 2 ) / (Na 2 O + K 2 O + Li 2 O)] are in the range of 1.39 to 1.80, and the refractive index nd is 1.78 to 1 It is possible to provide an optical glass having excellent devitrification resistance having a high refractive index and a high dispersion characteristic in a range of .83 and an Abbe number ⁇ d of 20 to 25.
- the optical glass according to aspect 1 can exhibit a liquidus temperature of 1050 ° C. or lower by adjusting the composition described above.
- the optical glass according to aspect 1 satisfies the following one or more glass compositions.
- the mass ratio [SiO 2 / (SiO 2 + P 2 O 5 + B 2 O 3 )] is 0.12 or less; Li 2 O content is 0 mass% or more and less than 0.3 mass%; The mass ratio [Li 2 O / (Na 2 O + K 2 O + Li 2 O)] is less than 0.0115; Li 2 O content is 0 mass% or more and less than 0.3 mass%; The mass ratio [(P 2 O 5 + B 2 O 3 + SiO 2 ) / (TiO 2 + Nb 2 O 5 + WO 3 + Bi 2 O 3 + Ta 2 O 5 )] is 0.49 or more.
- P 2 O 5 , B 2 O 3 and TiO 2 are essential components, and SiO 2 , Li 2 O, Nb 2 O 5 , WO 3 , Bi 2 O 3 , and Ta 2 O 5 are In the glass composition which is an optional component, P 2 O 5 content is 20 to 34% by mass, B 2 O 3 content is more than 0% by mass and 10% by mass or less, Li 2 O content is 0% by mass to less than 0.3% by mass, B 2 O 3 / P 2 O 5 ) greater than 0 and less than 0.39, mass ratio [(P 2 O 5 + B 2 O 3 ) / (TiO 2 + Nb 2 O 5 + WO 3 + Bi 2 O 3 + Ta 2 O 5 )] Exceeds 0.53, and the mass ratio [TiO 2 / (TiO 2 + Nb 2 O 5 + WO 3 + Bi 2 O 3 + Ta 2 O 5 )] is in the range of 0.059 to 0.96 (glass 2-A), Or P 2 O 5 content is 20 to 34%
- P 2 O 5 content is 20 to 34% by mass
- B 2 O 3 content is more than 0% by mass and 10% by mass or less
- Li 2 O content is 0% by mass to less than 0.3% by mass
- mass ratio [(P 2 O 5 + B 2 O 3 + SiO 2 ) / (TiO 2 + Nb 2 O 5 + WO 3 + Bi 2 O 3 + Ta 2) O 5 )] is 0.6 or more and the mass ratio [TiO 2 / (TiO 2 + Nb 2 O 5 + WO 3 + Bi 2 O 3 + Ta 2 O 5 )] is in the range of 0.059 to 0.96 (glass 2-C ),
- an optical glass having excellent devitrification resistance having a high refractive index and a high dispersion characteristic in which the refractive index nd is in the range of 1.78 to 1.83 and the Abbe number ⁇ d is in the range of 20 to 25. Can be obtained.
- the optical glass according to aspect 2 can exhibit a liquidus temperature of 1050 ° C. or lower by adjusting the composition described above.
- the glass 2-A has a mass ratio [SiO 2 / (SiO 2 + P 2 O 5 + B 2 O 3 )]. Preferably it is less than 0.02.
- the optical glass according to the aspect 2 satisfies one or more of the following glass compositions.
- the Nb 2 O 5 content is in the range of 19-47% by weight;
- the TiO 2 content is in the range of 6-24% by weight;
- the alkali metal oxide content is in the range of 10-30% by weight; Na 2 O content is in the range of 0-16% by mass; K 2 O content is in the range of 0-6% by mass; Bi 2 O 3 content is in the range of 0-15% by mass;
- the WO 3 content is in the range of 0 to 15% by mass.
- optical glass according to aspects 1 and 2 described above can suppress devitrification in any of the direct press method, the reheat press method, and the precision press method, the optical element blank, the glass material for press molding, and the optical It is suitable as glass for obtaining an element.
- an optical element blank made of the optical glass according to Aspect 1 or Aspect 2 a glass material for press molding, and an optical element are provided.
- Aspects 1 and 2 there is provided a method for producing a press-molding glass material comprising a step of molding the optical glass according to Aspect 1 or Aspect 2 into a press-molding glass material.
- manufacture of an optical element blank provided with the process of producing an optical element blank by press-molding using the press molding die in the state which softened the glass material for press molding mentioned above by heating.
- a method is also provided.
- an optical element manufacturing method including a step of manufacturing an optical element by grinding and / or polishing the above-described optical element blank.
- an optical element manufacturing method including a step of producing an optical element by press molding using a press mold in a state where the glass material for press molding is softened by heating. Is done.
- P 2 O 5 is 24 to 34%
- B 2 O 3 is more than 0% and 4% or less
- Li 2 O, Na 2 O and K 2 O are combined in a total of 12 to 20%
- Nb In a glass composition containing 15-30% 2 O 5 , 8-15% TiO 2 and 4-25% by mass Bi 2 O 3 , the mass ratio (TiO 2 / Nb 2 O 5 ) is 0.36-1.
- the refractive index nd is 1.78 or more and less than 1.83
- the Abbe number ⁇ d is An optical glass suitable for precision press molding having a high refractive index and high dispersion characteristic of 20 to 25 can be obtained.
- the optical glass according to the aspect 3 includes Li 2 O, Na 2 O, K 2 O, MgO, CaO, SrO, and BaO in a total of 12 to 17%. It is preferable to include in a range.
- the optical glass according to aspect 3 has a mass ratio (B 2 O 3 / P 2 O 5 ) in the range of more than 0 and 0.1 or less from the viewpoint of realizing a glass transition temperature suitable for precision press molding. preferable. From the same viewpoint, it is also preferable that the mass ratio (WO 3 / Nb 2 O 5 ) is in the range of 0.12 to 0.92, and the WO 3 content is in the range of 3 to 23% by mass.
- the CaO content is less than 1% by mass, and the total content of MgO, CaO, SrO, and BaO is less than 2% by mass.
- the optical glass according to Aspect 3 can have a glass transition temperature Tg of 520 ° C. or lower suitable for precision press molding by adjusting the composition described above.
- the optical glass according to the aspect 3 has glass characteristics such as low Tg suitable for precision press molding, a precision press molding preform and an optical element obtained by precision press molding the preform are obtained. It is suitable as the glass.
- Aspect 3 a precision press-molding preform and an optical element made of the optical glass according to Aspect 3 are provided.
- an optical element manufacturing method including a step of manufacturing an optical element by precision press molding using a press mold in a state where the above-described precision press molding preform is softened by heating. Provided.
- the optical glass according to one embodiment of the present invention can be obtained by performing the composition adjustment described in the specification on the glass composition exemplified above.
- the composition adjustment described in the specification on the glass composition exemplified above.
- the present invention is useful in the field of manufacturing various optical elements such as glass lenses, lens arrays, diffraction gratings, and prisms.
Abstract
Description
しかしながら、ガラスのネットワークフォーマーとしてリン酸を多く含むとともに、高屈折率付与成分および高分散性付与成分を含む組成の光学ガラスは、一般に失透傾向が強い。そのため、高屈折率・高分散特性を有するリン酸系光学ガラスにおける耐失透性を向上することは、従来困難であった。
更に本発明の一態様によれば、上述の光学ガラスからなる光学ガラスブランク、プレス成形用ガラス素材、光学素子、およびそれらの製造方法も提供される。
P2O5含有量が20~34質量%、
B2O3含有量が0質量%超かつ10質量%以下、
質量比(B2O3/P2O5)が0超かつ0.39未満、
質量比[TiO2/(TiO2+Nb2O5+WO3+Bi2O3+Ta2O5)]が0.059~0.180の範囲、
質量比[(P2O5+B2O3+SiO2)/(Na2O+K2O+Li2O)]が1.39~1.80の範囲、
であり、屈折率ndが1.78~1.83の範囲であり、かつアッベ数νdが20~25の範囲である光学ガラス、
に関する。
酸化物基準のガラス組成において、
P2O5、B2O3およびTiO2が必須成分であり、SiO2、Li2O、Nb2O5、WO3、Bi2O3、およびTa2O5が任意成分であり、
P2O5含有量が20~34質量%、
B2O3含有量が0質量%超かつ10質量%以下、
Li2O含有量が0質量%以上0.3質量%未満、
質量比(B2O3/P2O5)が0超かつ0.39未満、
質量比[(P2O5+B2O3)/(TiO2+Nb2O5+WO3+Bi2O3+Ta2O5)]が0.53超、
質量比[TiO2/(TiO2+Nb2O5+WO3+Bi2O3+Ta2O5)]が0.059~0.96の範囲、
であり、屈折率ndが1.78~1.83の範囲であり、かつアッベ数νdが20~25の範囲である光学ガラス(以下、「ガラス2-A」と記載する。);
酸化物基準のガラス組成において、
P2O5、B2O3およびTiO2が必須成分であり、SiO2、Li2O、Nb2O5、WO3、Bi2O3、およびTa2O5が任意成分であり、
P2O5含有量が20~34質量%、
B2O3含有量が0質量%超かつ10質量%以下、
Li2O含有量が0質量%以上0.3質量%未満、
質量比(B2O3/P2O5)が0超かつ0.39未満、
質量比[(P2O5+B2O3+SiO2)/(TiO2+Nb2O5+WO3+Bi2O3+Ta2O5)]が0.53超、
質量比[SiO2/(SiO2+P2O5+B2O3)]が0.02未満、
質量比[TiO2/(TiO2+Nb2O5+WO3+Bi2O3+Ta2O5)]が0.059~0.96の範囲、
であり、屈折率ndが1.78~1.83の範囲であり、かつアッベ数νdが20~25の範囲である光学ガラス(以下、「ガラス2-B」と記載する)、
を包含する。
更に本発明の一態様によれば、上述の光学ガラスからなる精密プレス成形用プリフォームおよび光学素子、ならびにこの精密プレス成形用プリフォームを精密プレス成形する光学素子の製造方法が提供される。
P2O5 24~34質量%、
B2O3 0質量%超4質量%以下、
Na2O、K2O、およびLi2Oを合計で12~20質量%、
Nb2O5 15~30質量%、
TiO2 8~15質量%、
Bi2O3 4~25質量%、
を含み、
質量比(TiO2/Nb2O5)が0.36~1.00の範囲であり、
質量比(Bi2O3/Nb2O5)が0.16~1.67の範囲であり、
屈折率ndが1.78以上1.83未満、かつアッベ数νdが20~25の範囲である光学ガラス、
に関する。
前述の通り、本発明では光学ガラスのガラス組成を酸化物基準で表示する。ここで「酸化物基準のガラス組成」とは、ガラス原料が熔融時にすべて分解されて光学ガラス中で酸化物として存在するものとして換算することにより得られるガラス組成をいうものとする。また、特記しない限り、ガラス組成は質量基準で表示するものとする。
本発明におけるガラス組成は、ICP-AES(Inductively Coupled Plasma - Atomic Emission Spectrometry)により求められたものである。また、本分析方法により求められた分析値は、±5%程度の測定誤差を含んでいる。
また、本明細書および本発明において、構成成分の含有量が0%とは、この構成成分を実質的に含まないことを意味し、この構成成分の含有量が不純物レベル程度以下であることを指す。
以下、態様1、態様2および態様3について説明する。特記しない限り、ある態様に関する記載は、他の態様についても適用可能である。また、態様1~3のいずれか2つ以上に該当する光学ガラスも、本発明の一態様にかかる光学ガラスに包含される。
態様1にかかる光学ガラスは、酸化物基準のガラス組成において、P2O5含有量が20~34質量%、B2O3含有量が0質量%超かつ10質量%以下、質量比(B2O3/P2O5)が0超かつ0.39未満、質量比[TiO2/(TiO2+Nb2O5+WO3+Bi2O3+Ta2O5)]が0.059~0.180の範囲、質量比[(P2O5+B2O3+SiO2)/(Na2O+K2O+Li2O)]が1.39~1.80の範囲であり、屈折率ndが1.78~1.83の範囲であり、かつアッベ数νdが20~25の範囲である光学ガラスである。
以下、その詳細について説明する。
ここでB2O3含有量が0%とは、B2O3がガラス中に不純物レベル程度に微量に含有されている場合を含む。したがって、B2O3含有量0%超とは、B2O3が不純物レベル程度を超えて含有されていることを指す。具体的には、例えば700ppm(質量比)以上、または1000ppm(質量比)以上である。
また、耐失透性向上と溶解性の観点からは、SiO2、P2O5およびB2O3の合計含入量に対するSiO2含有量の質量比[SiO2/(SiO2+P2O5+B2O3)]は、0.12以下であることが好ましく、0~0.04の範囲であることが、より好ましい。
また、Na2O含有量は、例えば0%以上とすることができ、8%以上であることが好ましく、11%以上であることがより好ましい。K2O含有量は、例えば0%以上とすることができ、2%以上であることが好ましく、3%以上であることがより好ましい。
耐失透性の観点からは、上述の光学ガラスのNa2O含有量は、例えば16%以下とすることができ、15%以下であることが好ましく、14%以下であることがより好ましい。同様の観点から、K2O含有量は、6%以下とすることが好ましく、より好ましくは5%以下である。
アルカリ金属酸化物の含有量(複数種含む場合には、それらの合計含有量)は、10%以上とすることが好ましく、耐失透性維持の観点からは、30%以下とすることが好ましく、20%以下とすることがより好ましい。好ましい下限は15%である。
また、各アルカリ土類金属酸化物の含有量については、MgO含有量の好ましい下限値は0%以上であり、好ましい上限値は5%以下である。CaO含有量は好ましい下限値は0%以上であり、好ましい上限値は1%未満である。SrO含有量の好ましい下限値は0%以上であり、好ましい上限値は5%以下である。BaO含有量の好ましい下限値は0%以上であり、好ましい上限値は7%未満であり、より好ましくは6%以下である。
液相温度の低いガラスは、軟化点付近での失透安定性が高いため、リヒートプレスのための加熱や精密プレス成形における加熱においてガラス中に結晶が析出することを防ぐことができる。また、液相温度の低いガラスは、低温で流出させることができるため、熔融ガラスを流出する際の温度を低くすることができる。ここでの温度を低くすることにより、ダイレクトプレス法による光学素子ブランク作製時や精密プレス成形法に用いるプレス成形用ガラス素材の作製時においてガラス中に結晶が析出することを防ぐことが可能となる。
また、熔融ガラスを流出する際の温度を低くすることにより、揮発による脈理発生を抑えること、および光学特性変動を低減することもできる。
更に、液相温度を低くすることにより、熔解を行うルツボのガラスによる侵蝕を抑えることができる。その結果、ルツボを構成する白金などの物質が、侵蝕によってガラス中に混入し異物となることや、イオンとして溶け込んでガラスの着色を引き起こすことを回避することができる。
次に、態様2について説明する。
態様2にかかる光学ガラスは、上述のガラス2-Aおよび2-Bを包含する。以下、その詳細について説明する。特記しない限り、下記記載は、ガラス2-Aおよび2-Bの両ガラスに適用される。
ここでB2O3含有量が0%とは、B2O3がガラス中に不純物レベル程度に微量に含有されている場合を含む。したがって、B2O3含有量0%超とは、B2O3が不純物レベル程度を超えて含有されていることを指す。具体的には、例えば700ppm(質量比)以上、または1000ppm(質量比)以上である。
また、Na2O含有量は、例えば0%以上とすることができ、8%以上であることが好ましく、11%以上であることがより好ましい。K2O含有量は、例えば0%以上とすることができ、2%以上であることが好ましく、3%以上であることがより好ましい。
耐失透性の観点からは、上述の光学ガラスのNa2O含有量は、例えば16%以下とすることができ、15%以下であることが好ましく、14%以下であることがより好ましい。同様の観点から、K2O含有量は、6%以下とすることが好ましく、より好ましくは5%以下である。
アルカリ金属酸化物の含有量(複数種含む場合には、それらの合計含有量)は、10%以上とすることが好ましく、耐失透性維持の観点からは、30%以下とすることが好ましく、20%以下とすることがより好ましい。好ましい下限は15%である。
また、各アルカリ土類金属酸化物の含有量については、MgO含有量の好ましい下限値は0%以上であり、好ましい上限値は5%以下である。CaO含有量は好ましい下限値は0%以上であり、好ましい上限値は1%未満である。SrO含有量の好ましい下限値は0%以上であり、好ましい上限値は 5 %以下である。BaO含有量の好ましい下限値は0%以上であり、好ましい上限値は7%未満であり、より好ましくは6%以下である。
液相温度の低いガラスは、軟化点付近での失透安定性が高いため、リヒートプレスのための加熱や精密プレス成形における加熱においてガラス中に結晶が析出することを防ぐことができる。また、液相温度の低いガラスは、低温で流出させることができるため、熔融ガラスを流出する際の温度を低くすることができる。ここでの温度を低くすることにより、ダイレクトプレス法による光学素子ブランク作製時や精密プレス成形法に用いるプレス成形用ガラス素材の作製時においてガラス中に結晶が析出することを防ぐことが可能となる。
また、熔融ガラスを流出する際の温度を低くすることにより、揮発による脈理発生を抑えること、および光学特性変動を低減することもできる。
更に、液相温度を低くすることにより、熔解を行うルツボのガラスによる侵蝕を抑えることができる。その結果、ルツボを構成する白金などの物質が、侵蝕によってガラス中に混入し異物となることや、イオンとして溶け込んでガラスの着色を引き起こすことを回避することができる。
次に、態様3について説明する。
態様3にかかる光学ガラスは、酸化物基準のガラス組成において、P2O5を24~34質量%、B2O3を0質量%超4質量%以下、Na2O、K2O、およびLi2Oを合計で12~20質量%、Nb2O5を15~30質量%、TiO2を8~15質量%、Bi2O3を4~25質量%含み、質量比(TiO2/Nb2O5)が0.36~1.00の範囲であり、質量比(Bi2O3/Nb2O5)が0.16~1.67の範囲であり、屈折率ndが1.78以上1.83未満、かつアッベ数νdが20~25の範囲である光学ガラスである。
以下、その詳細について説明する。
ここで、B2O3含有量0%とは、B2O3がガラス中に不純物レベル程度に微量に含有されている場合を含む。したがって、B2O3含有量が0%超とは、B2O3が不純物レベル程度を超えて含有されていることを指す。具体的には、例えば700ppm(質量比)以上、または1000ppm(質量比)以上である。
以上の点から、上述の光学ガラスは、比較的低いガラス転移温度、具体的には520℃以下のガラス転移温度を有することが好ましい。ガラス転移温度は、より好ましくは510℃以下、更に好ましくは500℃以下、一層好ましくは490℃以下である。また、ガラス安定性の観点からは、ガラス転移温度は460℃超であることが好ましく、465℃以上であることがより好ましく、470℃以上であることが更に好ましい。
アルカリ金属酸化物とアルカリ土類金属酸化物の合計含有量(Li2O+Na2O+K2O+MgO+CaO+SrO+BaO)は、高屈折率・高分散特性を実現する観点からは、12~17%の範囲とすることが好ましい。上限値は、より好ましくは17%以下であり、更に好ましくは16%以下である。
また、各アルカリ土類金属酸化物の含有量については、MgO含有量の好ましい下限値は0%以上であり、好ましい上限値は2%以下である。CaO含有量は好ましい下限値は0%以上であり、好ましい上限値は2%以下であり、より好ましくは1%未満である。SrO含有量の好ましい下限値は0%以上であり、好ましい上限値は2%以下である。BaO含有量の好ましい下限値は0%以上であり、好ましい上限値は2%以下である。
nd≦15/νd+1.18 …(1)
先に説明した組成調整を行うことで、前述の範囲の屈折率ndおよびアッベ数νdを有するとともに、式(1)を満たす光学ガラスを得ることができる。
(A)Li2O、Na2O、K2O、MgO、CaO、SrOおよびBaOの合計含有量が12~17%の範囲であり、かつ質量比(B2O3/P2O5)が0超かつ0.1以下の範囲である組成。好ましくは、Li2O、Na2O、K2O、MgO、CaO、SrOおよびBaOの合計含有量が12~17%の範囲であり、かつ質量比(B2O3/P2O5)については、好ましくは0超かつ0.083以下の範囲である組成。
(B)Li2O、Na2O、K2O、MgO、CaO、SrOおよびBaOの合計含有量が12~17%の範囲であり、かつ質量比(Bi2O3/Nb2O5)が0.16~1.67の範囲である組成。好ましくは、Li2O、Na2O、K2O、MgO、CaO、SrOおよびBaOの合計含有量が12~17%の範囲であり、かつ質量比(Bi2O3/Nb2O5)が0.16~0.87の範囲である組成。
(C)Li2O、Na2O、K2O、MgO、CaO、SrOおよびBaOの合計含有量が12~17%の範囲であり、かつ質量比(WO3/Nb2O5)が0.12~0.92の範囲である組成。
(D)Li2O、Na2OおよびK2Oの合計含有量が12~20%の範囲であり、かつ質量比(WO3/Nb2O5)が0.12~0.92の範囲である組成。
(E)Li2O、Na2O、K2O、MgO、CaO、SrOおよびBaOの合計含有量が12~20%の範囲であり、かつ質量比(WO3/Nb2O5)が0.12~0.92の範囲である組成。
(F)質量比(TiO2/Nb2O5)が0.36~1.00の範囲であり、かつLi2O、Na2O、K2O、MgO、CaO、SrOおよびBaOの合計含有量が12~17%の範囲である組成。好ましくは、質量比(TiO2/Nb2O5)が0.40~0.80の範囲であり、かつLi2O、Na2O、K2O、MgO、CaO、SrOおよびBaOの合計含有量の好ましい範囲は12~17%の範囲である組成。
<態様1、態様2>
本発明の他の一態様は、
態様1または態様2にかかる光学ガラスからなる光学素子ブランク;
態様1または態様2にかかる光学ガラスからなるプレス成形用ガラス素材;
態様1または態様2にかかる光学ガラスをプレス成形用ガラス素材に成形する工程を備えるプレス成形用ガラス素材の製造方法;および、
上述のプレス成形用ガラス素材を加熱により軟化した状態で、プレス成形型を用いてプレス成形することにより光学素子ブランクを作製する工程を備える光学素子ブランクの製造方法、
に関する。
本発明の他の一態様は、
態様1または態様2にかかる光学ガラスからなる光学素子;
上述の光学素子ブランクを研削および/または研磨することにより光学素子を作製する工程を備える光学素子の製造方法(以下、「方法A」という);
上述のプレス成形用ガラス素材を加熱により軟化した状態で、プレス成形型を用いてプレス成形することにより光学素子を作製する工程を備える光学素子の製造方法(以下、「方法B」という)、
に関する。
[精密プレス成形用プリフォーム]
態様3は、上述の光学ガラスからなる精密プレス成形用プリフォームにも関する。精密プレス成形用プリフォーム(以下、プリフォームともいう)は、精密プレス成形に供されるガラス塊を意味し、精密プレス成形品の質量に相当するガラス成形体である。また、精密プレス成形については、先に記載した通りである。
本発明の他の一態様は、
態様3にかかる光学ガラスからなる光学素子;および、
上述の精密プレス成形用プリフォームを加熱により軟化した状態で、プレス成形型を用いて精密プレス成形することにより光学素子を作製する工程を備える光学素子の製造方法、
に関する。
下記表に示す組成の光学ガラスが得られるように、各ガラス成分に対応する酸化物、炭酸塩、硫酸塩、硝酸塩、水酸化物等のガラス原料を所定の割合に150~300g秤量し、十分に混合して調合バッチとした。これを白金ルツボに入れ、1000~1250℃で攪拌しながら空気中で2~4時間、ガラスの熔解を行った。熔解後、熔融ガラスを40×70×15mmのカーボンの金型に流し、ガラス転移温度まで放冷してから直ちにアニール炉に入れ、ガラスの転移温度範囲で約1時間アニールして炉内で室温まで放冷し、各光学ガラスを作製した。
下記方法により、各光学ガラスの屈折率、アッベ数、ガラス転移温度、および液相温度を測定した。
(1)屈折率(nd)およびアッべ数(νd)
徐冷降温速度を-30℃/時にして得られた光学ガラスについて測定した。
(2)ガラス転移温度Tg
示差走査熱量計(DSC(Differential Scanning Calorimetry))により、昇温速度10℃/分にして測定した。
(3)液相温度LT
ガラス試料任意温度に設定した試験炉に2時間保持し、倍率10~100倍の光学顕微鏡により結晶の有無を観察し、液相温度を測定した。
(4)失透性評価
下記表中、失透性評価を行ったガラス試料については、以下の方法により耐失透性を評価した。
1cm角ガラス試料を、そのガラスのガラス転移温度Tgに設定した第1の試験炉で10分間加熱し、さらにそのガラスのTgプラス10℃に設定した第2の試験炉に10分間加熱した後、結晶または白濁の有無を光学顕微鏡(観察倍率:10~100倍)で確認した。結晶も白濁も確認されなかった場合は○、結晶および白濁の少なくとも一方が確認された場合は×と判定した。本明細書では、耐失透性の指標として、以上の評価結果を用いた。
本発明の一態様にかかる光学ガラスとはガラス組成が相違する特開平6-345481号公報記載の実施例4についても同様の評価を行ったところ、ndは1.72914、νdは26.22であり、上述の光学ガラスが満たす光学特性を有さないことが確認された。
上述のプリフォームの表面に必要に応じてコーティングを施し、成形面に炭素系離型膜を設けたSiC製の上下型および胴型を含むプレス成形型内に導入し、窒素雰囲気中で成形型とプリフォームを一緒に加熱してプリフォームを軟化し、精密プレス成形して上記各種ガラスからなる非球面凸メニスカスレンズ、非球面凹メニスカスレンズ、非球面両凸レンズ、非球面両凹レンズの各種レンズを作製した。なお、精密プレス成形の各条件は前述の範囲で調整した。
上述の態様1にかかる実施例および態様2にかかる実施例の各ガラスが得られる清澄、均質化した熔融ガラスを用意し、白金製パイプから一定流量で連続して流出し、パイプ下方に水平に配置した一側壁が開口した鋳型に流し込み、一定の幅を厚みを有するガラス板に成形しつつ、鋳型の開口部から成形したガラス板を引き出した。引き出されたガラス板を、アニール炉内でアニール処理し、歪を低減し、脈理や異物が無く、着色の少ない上記各光学ガラスからなるガラス板を得た。
次に、これら各ガラス板を縦横に切断し、同一寸法を有する直方体形状のガラス片を複数個得た。さらに複数個のガラス片をバレル研磨して、目的とするプレス成形品の重量にあわせ、プレス成形用ガラスゴブとした。
なお、上述の方法とは別に、熔融ガラスを一定流速で白金製ノズルから流出し、このノズルの下方に多数の受け型を次々と移送して所定質量の熔融ガラス塊を次々と受け、これら熔融ガラス塊を球または回転体形状に成形し、アニール処理してからバレル研磨して目的とするプレス成形品の質量にあわせ、プレス成形用ガラスゴブとしてもよい。
このようなレンズにより、良好な撮像光学系を構成することができる。
なお、プレス成形型の形状、ガラスゴブの体積を適宜設定することにより、プリズム等その他の光学素子を製造することもできる。
Li2O含有量が0質量%以上0.3質量%未満である;
質量比[Li2O/(Na2O+K2O+Li2O)]が0.0115未満である;
Li2O含有量が0質量%以上0.3質量%未満である;
質量比[(P2O5+B2O3+SiO2)/(TiO2+Nb2O5+WO3+Bi2O3+Ta2O5)]が0.49以上である。
P2O5含有量を20~34質量%、B2O3含有量を0質量%超かつ10質量%以下、Li2O含有量を0質量%以上0.3質量%未満、質量比(B2O3/P2O5)を0超かつ0.39未満、質量比[(P2O5+B2O3)/(TiO2+Nb2O5+WO3+Bi2O3+Ta2O5)]を0.53超、質量比[TiO2/(TiO2+Nb2O5+WO3+Bi2O3+Ta2O5)]を0.059~0.96の範囲(ガラス2-A)、または、
P2O5含有量を20~34質量%、B2O3含有量を0質量%超かつ10質量%以下、Li2O含有量が0質量%以上0.3質量%未満、
質量比(B2O3/P2O5)を0超かつ0.39未満、質量比[(P2O5+B2O3+SiO2)/(TiO2+Nb2O5+WO3+Bi2O3+Ta2O5)]を0.53超、質量比[SiO2/(SiO2+P2O5+B2O3)]を0.02未満、質量比[TiO2/(TiO2+Nb2O5+WO3+Bi2O3+Ta2O5)]を0.059~0.96の範囲(ガラス2-B)、
とすることにより、屈折率ndが1.78~1.83の範囲、かつアッベ数νdが20~25の範囲の高屈折率・高分散特性を有する、優れた耐失透性を有する光学ガラスを得ることができる。
P2O5含有量を20~34質量%、B2O3含有量を0質量%超かつ10質量%以下、Li2O含有量を0質量%以上0.3質量%未満、質量比(B2O3/P2O5)を0超かつ0.39未満、質量比[(P2O5+B2O3+SiO2)/(TiO2+Nb2O5+WO3+Bi2O3+Ta2O5)]を0.6以上、質量比[TiO2/(TiO2+Nb2O5+WO3+Bi2O3+Ta2O5)]を0.059~0.96の範囲(ガラス2-C)、
とすることによって、屈折率ndが1.78~1.83の範囲、かつアッベ数νdが20~25の範囲の高屈折率・高分散特性を有する、優れた耐失透性を有する光学ガラスを得ることができる。
ガラス2-Cの詳細については、ガラス2-A、2-Bに関する上述の記載を適用することができる。
Nb2O5含有量が19~47質量%の範囲である;
TiO2含有量が6~24質量%の範囲である;
アルカリ金属酸化物の含有量が10~30質量%の範囲である;
Na2O含有量が0~16質量%の範囲である;
K2O含有量が0~6質量%の範囲である;
Bi2O3含有量が0~15質量%の範囲である;
WO3含有量が0~15質量%の範囲である。
例えば、上述の例示されたガラス組成に対し、明細書に記載の組成調整を行うことにより、本発明の一態様にかかる光学ガラスを得ることができる。
また、明細書に例示または好ましい範囲として記載した事項の2つ以上を任意に組み合わせることは、もちろん可能である。
Claims (34)
- 酸化物基準のガラス組成において、
P2O5含有量が20~34質量%、
B2O3含有量が0質量%超かつ10質量%以下、
質量比(B2O3/P2O5)が0超かつ0.39未満、
質量比[TiO2/(TiO2+Nb2O5+WO3+Bi2O3+Ta2O5)]が0.059~0.180の範囲、
質量比[(P2O5+B2O3+SiO2)/(Na2O+K2O+Li2O)]が1.39~1.80の範囲、
であり、屈折率ndが1.78~1.83の範囲であり、かつアッベ数νdが20~25の範囲である光学ガラス。 - 質量比[SiO2/(SiO2+P2O5+B2O3)]が0.12以下である請求項1に記載の光学ガラス。
- Li2O含有量が0質量%以上0.3質量%未満である請求項1または2に記載の光学ガラス。
- 質量比[Li2O/(Na2O+K2O+Li2O)]が0.0115未満である請求項1~3のいずれか1項に記載の光学ガラス。
- 質量比[(P2O5+B2O3+SiO2)/(TiO2+Nb2O5+WO3+Bi2O3+Ta2O5)]が0.49以上である請求項1~4のいずれか1項に記載の光学ガラス。
- 1050℃以下の液相温度を有する請求項1~5のいずれか1項に記載の光学ガラス。
- 酸化物基準のガラス組成において、
P2O5、B2O3およびTiO2が必須成分であり、SiO2、Li2O、Nb2O5、WO3、Bi2O3、およびTa2O5が任意成分であり、
P2O5含有量が20~34質量%、
B2O3含有量が0質量%超かつ10質量%以下、
Li2O含有量が0質量%以上0.3質量%未満、
質量比(B2O3/P2O5)が0超かつ0.39未満、
質量比[(P2O5+B2O3)/(TiO2+Nb2O5+WO3+Bi2O3+Ta2O5)]が0.53超、
質量比[TiO2/(TiO2+Nb2O5+WO3+Bi2O3+Ta2O5)]が0.059~0.96の範囲、
であり、屈折率ndが1.78~1.83の範囲であり、かつアッベ数νdが20~25の範囲である光学ガラス。 - 質量比[SiO2/(SiO2+P2O5+B2O3)]が0.02未満である請求項7に記載の光学ガラス。
- 酸化物基準のガラス組成において、
P2O5、B2O3およびTiO2が必須成分であり、SiO2、Li2O、Nb2O5、WO3、Bi2O3、およびTa2O5が任意成分であり、
P2O5含有量が20~34質量%、
B2O3含有量が0質量%超かつ10質量%以下、
Li2O含有量が0質量%以上0.3質量%未満、
質量比(B2O3/P2O5)が0超かつ0.39未満、
質量比[(P2O5+B2O3+SiO2)/(TiO2+Nb2O5+WO3+Bi2O3+Ta2O5)]が0.53超、
質量比[SiO2/(SiO2+P2O5+B2O3)]が0.02未満、
質量比[TiO2/(TiO2+Nb2O5+WO3+Bi2O3+Ta2O5)]が0.059~0.96の範囲、
であり、屈折率ndが1.78~1.83の範囲であり、かつアッベ数νdが20~25の範囲である光学ガラス。 - 1050℃以下の液相温度を有する請求項7~9のいずれか1項に記載の光学ガラス。
- Nb2O5含有量が19~47質量%の範囲である請求項7~10のいずれか1項に記載の光学ガラス。
- TiO2含有量が6~24質量%の範囲である請求項7~11のいずれか1項に記載の光学ガラス。
- アルカリ金属酸化物の含有量が10~30質量%の範囲である請求項7~12のいずれか1項に記載の光学ガラス。
- Na2O含有量が0~16質量%の範囲、
K2O含有量が0~6質量%の範囲、
である請求項7~13のいずれか1項に記載の光学ガラス。 - Bi2O3含有量が0~15質量%の範囲である請求項7~14のいずれか1項に記載の光学ガラス。
- WO3含有量が0~15質量%の範囲である請求項7~15のいずれか1項に記載の光学ガラス。
- 請求項1~16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1~16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素材。
- 請求項1~16のいずれか1項に記載の光学ガラスからなる光学素子。
- 請求項1~16のいずれか1項に記載の光学ガラスをプレス成形用ガラス素材に成形する工程を備えるプレス成形用ガラス素材の製造方法。
- 請求項18に記載のプレス成形用ガラス素材を、プレス成形型を用いてプレス成形することにより光学素子ブランクを作製する工程を備える光学素子ブランクの製造方法。
- 請求項17に記載の光学素子ブランクを研削および/または研磨することにより光学素子を作製する工程を備える光学素子の製造方法。
- 請求項18に記載のプレス成形用ガラス素材を、プレス成形型を用いてプレス成形することにより光学素子を作製する工程を備える光学素子の製造方法。
- 酸化物基準のガラス組成において、
P2O5 24~34質量%、
B2O3 0質量%超4質量%以下、
Li2O、Na2OおよびK2Oを合計で12~20質量%、
Nb2O5 15~30質量%、
TiO2 8~15質量%、
Bi2O3 4~25質量%、
を含み、
質量比(TiO2/Nb2O5)が0.36~1.00の範囲であり、
質量比(Bi2O3/Nb2O5)が0.16~1.67の範囲であり、
屈折率ndが1.78以上1.83未満、かつアッベ数νdが20~25の範囲である光学ガラス。 - Li2O、Na2O、K2O、MgO、CaO、SrOおよびBaOの合計含有量が12~17質量%の範囲である請求項24に記載の光学ガラス。
- 質量比(B2O3/P2O5)が0超かつ0.1以下の範囲である請求項24または25に記載の光学ガラス。
- 質量比(WO3/Nb2O5)が0.12~0.92の範囲である請求項24~26のいずれか1項に記載の光学ガラス。
- WO3含有量が3~23質量%の範囲である請求項24~27のいずれか1項に記載の光学ガラス。
- CaO含有量が1質量%未満である請求項24~28のいずれか1項に記載の光学ガラス。
- MgO、CaO、SrO、およびBaOの合計含有量が2質量%未満である請求項24~29のいずれか1項に記載の光学ガラス。
- ガラス転移温度Tgが520℃以下である請求項24~30のいずれか1項に記載の光学ガラス。
- 請求項24~31のいずれか1項に記載の光学ガラスからなる精密プレス成形用プリフォーム。
- 請求項24~31のいずれか1項に記載の光学ガラスからなる光学素子。
- 請求項32に記載の精密プレス成形用プリフォームを加熱により軟化した状態で、プレス成形型を用いて精密プレス成形することにより光学素子を作製する工程を備える光学素子の製造方法。
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