Method for manufacturing optical glass

Abstract

To provide a method for manufacturing optical glass that can shorten heat treatment time for optical glass after molding process.SOLUTION: A method for manufacturing optical glass includes: a blending step of mixing raw materials; a melting step of melting the raw materials and making molten glass; and a molding step of molding the molten glass while increasing viscosity of the molten glass. In the molding step, water content is supplied to the glass.SELECTED DRAWING: Figure 1

Description

[Background technology]

[0001] In recent years, the digitalization and high-definition capabilities of devices using optical systems have progressed rapidly. In the fields of various optical equipment, such as photographic equipment like digital cameras and video cameras, and image playback (projection) equipment like projectors and projection televisions, there is a growing demand to reduce the number of optical elements such as lenses and prisms used in the optical system, thereby making the entire optical system lighter and smaller.

[0002] In the manufacturing of optical glass, if the glass contains components such as TiO2, Nb2O5, and WO3, these components are easily reduced during the melting process. This can lead to discoloration of the glass after slow cooling, but it is known that heat treatment can improve this discoloration.

[0003] For example, Patent Document 1 describes a manufacturing method for phosphate-based glass containing a large amount of high refractive index components such as TiO2, Nb2O5, and WO3, in which the color improvement effect of the glass after heat treatment can be improved by performing a process in which water vapor is added to the molten atmosphere and a process in which water vapor is bubbled into the molten material during the melting process. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2016-190788 [Overview of the project] [Problems that the invention aims to solve]

[0005] Patent Document 1 discloses that adding water during the melting process increases the water content in the glass, thereby improving the color of the glass after heat treatment. However, it is known that excessive water supply to the glass can have effects such as changes in refractive index and accelerated crystallization, making it necessary to control the water content in order to produce stable glass. [Means for solving the problem]

[0006] To solve the above problems, the inventors conducted extensive testing and research, and as a result, discovered a method for manufacturing optical glass that shortens the heat treatment time of the optical glass after the molding process by supplying water during the molding process, where the effects of performance fluctuations and crystallization acceleration are minimal.

[0007] Specifically, the present invention provides the following: (1) A blending process in which raw materials are mixed, The melting process involves melting the raw materials to produce molten glass, A molding process that increases the viscosity of molten glass while shaping it. Includes A method for manufacturing optical glass, characterized by supplying water to the glass during the molding process.

[0008] (2) A method for manufacturing optical glass as described in (1), The aforementioned optical glass has an oxide-based composition in mass % of the total mass of the glass. P2O5 15-40% TiO20%~30% Nb2O560% or less, WO320% or less, A method for manufacturing optical glass, characterized by containing [the specified ingredient].

[0009] The present invention has been made in view of the above problems, and its objective is to obtain optical glass in which the heat treatment time is shortened while suppressing refractive index fluctuations and crystallization promotion by supplying moisture to the glass during the molding process.

[0010] According to the optical glass manufacturing method of the present invention, glass can be obtained in which the oxide contains P2O5 at 15-40%, TiO2 at 5-30%, Nb2O5 at 60% or less, and WO at 320% or less by mass%, and by supplying water to the glass during the molding process, thereby suppressing refractive index fluctuations and crystallization, and shortening the heat treatment time. [Modes for carrying out the invention]

[0011] Hereinafter, embodiments of the optical glass and the method for manufacturing the optical glass of the present invention will be described in detail. The present invention is not limited to the following embodiments, and can be implemented with appropriate modifications within the scope of the object of the present invention. In addition, regarding the parts where the description overlaps, the description may be omitted as appropriate, but it does not limit the gist of the invention. (Glass components)

[0012] In this specification, unless otherwise specified, the content of each component is expressed as mass% with respect to the total mass of the oxide-converted composition. Here, the "oxide-converted composition" is a composition in which each component contained in the glass is expressed assuming that oxides, double salts, metal fluorides, etc. used as raw materials of the glass constituent components of the present invention are all decomposed into oxides during melting and the total mass of the generated oxides is 100 mass%.

[0013] The glass according to the present invention is a phosphate glass, and among the SiO2 component, B2O3 component, and P2O5 component known as network-forming oxides, it is a glass containing the most P2O5 component. The P2O5 component is a glass-forming component and a component that lowers the melting temperature of the glass. On the other hand, by setting the content of the P2O5 component to 40.0% or less, a desired refractive index and Abbe number can be obtained. On the other hand, the content of the P2O5 component with respect to the total mass of the glass in the oxide-converted composition is preferably 15.0% or more, more preferably 18.0% or more, still more preferably 20.0% or more as the lower limit, preferably 40.0% or less, more preferably 35.0% or less, and most preferably 30.0% or less as the upper limit. The P2O5 component can use Al(PO3)3, Ca(PO3)2, Ba(PO3)2, BPO4, H3PO 4、 NaH2PO4, KH2PO4, etc.

[0014] The Nb2O5 component is a component that increases the refractive index and lowers the Abbe number. Therefore, the lower limit of the Nb2O5 component content is preferably 35.0% or more, more preferably 38.0% or more, and even more preferably 40.0% or more. On the other hand, by reducing the Nb2O5 content to 60.0% or less, the material cost of the glass can be reduced, and its resistance to devitrification can be improved. Therefore, the Nb2O5 content is preferably limited to 60.0% or less, more preferably to 58.0% or less, and even more preferably to 55.0% or less. For the Nb2O5 component, Nb2O5 or similar materials can be used as raw materials.

[0015] The TiO2 component is a component that can increase the refractive index and lower the Abbe number. Therefore, the TiO2 component content is preferably more than 0%, more preferably 1.5% or more, even more preferably 3.0% or more, and even more preferably 5.0% or more as the lower limit. On the other hand, by limiting the TiO2 component content to 20.0% or less, the deterioration of transmittance on the short-wavelength side can be suppressed. Therefore, the TiO2 component content is preferably limited to 30.0% or less, more preferably to 25.0% or less, and even more preferably to 20.0% or less. The TiO2 component can use TiO2 or similar materials as raw materials.

[0016] The WO3 component enhances refractive index and devitrification resistance, and lowers the Abbe number. In particular, by limiting the WO3 component content to 20.0% or less, devitrification due to excessive content and a decrease in transmittance on the short-wavelength side can be suppressed. Therefore, the WO3 component content is preferably limited to 20.0% or less, more preferably to 15.0% or less, more preferably to 10.0% or less, and even more preferably to 6.0% or less.

[0017] The Na2O component, when present in amounts exceeding 0%, can improve the meltability of the glass raw material and enhance its transmittance. Therefore, the lower limit of the Na2O component content is preferably more than 0%, more preferably more than 0.1%, even more preferably more than 0.5%, even more preferably more than 1.0%, even more preferably more than 1.5%, and even more preferably more than 2.0%. On the other hand, by limiting the Na2O content to 15.0% or less, the decrease in the refractive index of the glass due to excessive content and devitrification can be reduced, and devitrification during reheat pressing can be suppressed. Therefore, the Na2O content is preferably limited to 15.0% or less, more preferably less than 12.0%, and even more preferably less than 10.0%. For the Na2O component, Na2CO3, NaNO3, NaF, Na2SO4, Na2SiF6, etc., can be used as raw materials.

[0018] The K2O component, when present in amounts exceeding 0%, enhances solubility and improves permeability. Therefore, the K2O content may be preferably greater than 0%, more preferably 0.5% or more, and even more preferably greater than 1.0% as the lower limit. On the other hand, by limiting the K2O content to 15.0% or less, the stability of the glass can be maintained and the decrease in refractive index can be suppressed. Therefore, the K2O content is preferably limited to 15.0% or less, more preferably to 12.0% or less, and even more preferably to less than 10.0%. The K2O component can be K2CO3, KNO3, KF, KHF2, K2SO4, K2SiF6, etc.

[0019] The Li2O component is an optional component that can improve the fusion properties of glass and lower the glass transition temperature. On the other hand, by reducing the content of the Li2O component, it is possible to make it less likely to lower the refractive index of the glass and to reduce devitrification of the glass and devitrification during reheat pressing. Therefore, the content of the Li2O component may be preferably 5.0% or less, more preferably less than 3.0%, even more preferably 1.0% or less, and even more preferably less than 0.5%. The Li2O component can be Li2CO3, Li2SO4, LiNO3, etc.

[0020] The BaO component, when present in amounts exceeding 0%, is an optional component that can enhance the meltability of the glass raw material, reduce devitrification of the glass, and increase the refractive index. Furthermore, among components that yield a high refractive index, it has low material costs and is easily melted. Therefore, the BaO component content is preferably set to a lower limit of more than 0%, more preferably more than 0.1%, even more preferably more than 0.2%, and even more preferably more than 0.5%. On the other hand, by limiting the BaO content to 15.0% or less, the decrease in the refractive index of the glass and devitrification caused by excessive content can be reduced. Therefore, the BaO content is preferably limited to 15.0% or less, more preferably less than 12.0%, and even more preferably less than 10.0%. The BaO component is derived from BaCO3, Ba(NO3)2, Ba(PO3)2, and BaF 2、 The following can be used.

[0021] MgO, CaO, and SrO are optional components that, when present in amounts exceeding 0%, can be used to adjust the refractive index, meltability, and devitrification resistance of the glass. On the other hand, by limiting the content of MgO, CaO, and SrO components to 5.0% or less, the decrease in refractive index can be suppressed, and devitrification due to excessive content of these components can be reduced. Therefore, the content of MgO, CaO, and SrO components is preferably limited to 5.0% or less, more preferably to 4.0% or less, and even more preferably to less than 3.0%. For the MgO, CaO, and SrO components, MgCO3, MgO, MgF2, CaCO3, CaF2, Sr(NO3)2, SrCO3, SrF2, etc. can be used as raw materials.

[0022] The SiO2 component is a glass-forming oxide component. When it is present in a concentration of more than 0%, it improves the viscosity of the molten glass and enhances its chemical durability. Therefore, the lower limit of the SiO2 component content is preferably more than 0%, more preferably more than 0.1%, and even more preferably more than 0.3%. On the other hand, by limiting the SiO2 content to 5.0% or less, the rise in the glass transition temperature and the decrease in refractive index can be suppressed. Therefore, the SiO2 content is preferably limited to 5.0% or less, more preferably to 4.0% or less, and even more preferably to less than 3.0%. For the SiO2 component, SiO2, K2SiF6, Na2SiF6, etc., can be used as raw materials.

[0023] The B2O3 component is an optional component used as a glass-forming oxide when present in amounts greater than 0%. On the other hand, by limiting the B2O3 content to 5.0% or less, the deterioration of devitrification during reheat pressing can be reduced, and the deterioration of chemical durability can be suppressed. Therefore, the B2O3 content is preferably limited to 5.0% or less, more preferably to 4.5% or less, and even more preferably to less than 4.0%. For the B2O3 component, H3BO3, Na2B4O7, Na2B4O7·10H2, BPO4, etc., can be used as raw materials.

[0024] ZnO is an optional component that, when present in amounts greater than 0%, can enhance the solubility of the raw materials, promote degassing from the molten glass, and improve the stability of the glass. On the other hand, by limiting the ZnO content to less than 5.0%, the decrease in refractive index can be suppressed, and devitrification due to excessive viscosity reduction can be reduced. Therefore, the ZnO content may be preferably limited to less than 5.0%, more preferably less than 4.0%, and even more preferably less than 3.0%. For the ZnO component, ZnO, ZnF2, etc., can be used as raw materials.

[0025] The ZrO2 component is an optional component that, when present in amounts greater than 0%, can increase the refractive index of the glass and reduce devitrification. Therefore, the ZrO2 content may preferably be greater than 0%, more preferably greater than 0.5%, and even more preferably greater than 1.0%. On the other hand, by limiting the ZrO2 content to 5.0% or less, devitrification due to excessive content can be reduced. Therefore, the ZrO2 content may be preferably 5.0% or less, more preferably 3.0% or less, even more preferably less than 1.0%, and even more preferably less than 0.5%. Furthermore, the ZrO2 component may not be included at all. For the ZrO2 component, ZrO2, ZrF4, etc., can be used as raw materials.

[0026] The La2O3, Gd2O, Y2O3, Yb2O3, and Ta2O5 components are optional components that, when present in amounts exceeding 0%, can increase the refractive index of the glass and improve its resistance to devitrification. On the other hand, by reducing the content of La2O3, Gd2O, Y2O3, Yb2O3, and Ta2O5 components to 5.0% or less, the raw material cost of optical glass can be reduced. Furthermore, the melting temperature of the raw materials is lowered, and the energy required for melting the raw materials is reduced, thus reducing the manufacturing cost of optical glass. Therefore, the total content of La2O3, Gd2O, Y2O3, Yb2O3, and Ta2O5 components may be preferably 5.0% or less, more preferably less than 3.0%, even more preferably less than 2.0%, and even more preferably less than 1.0%.

[0027] The Bi2O3 component is an optional component that, when present in amounts greater than 0%, can increase the refractive index, lower the Abbe number, and reduce the glass transition temperature. On the other hand, by reducing the Bi2O3 content to 5.0% or less, the liquidus temperature of the glass can be lowered, thereby improving its resistance to devitrification. Therefore, the Bi2O3 content may be preferably 5.0% or less, more preferably less than 3.0%, and even more preferably less than 1.0%. In particular, it is preferable not to include it at all from the viewpoint of obtaining glass with good transmittance. For the Bi2O3 component, Bi2O3 or similar materials can be used as raw materials.

[0028] The GeO2 component, when present in amounts exceeding 0%, enhances refractive index and resistance to devitrification. The GeO2 component content is preferably 3.0% or less, more preferably 2.0% or less, even more preferably 1.0% or less, and even more preferably 0.5% or less, with the most preferable being no GeO2 content at all. The GeO2 component can use GeO2 or similar as a raw material.

[0029] The TeO2 component enhances the melting properties of glass raw materials, increases the refractive index of glass, lowers the Abbe number, and lowers the glass transition temperature. On the other hand, a high TeO2 content worsens the transmittance. Therefore, the TeO2 content is preferably limited to 3.0% or less, more preferably 2.0% or less, even more preferably 1.0% or less, and even more preferably 0.5% or less, and most preferably not present at all. For the TeO2 component, TeO2 or similar materials can be used as raw materials.

[0030] The Ta2O5 component is a component that increases the refractive index. On the other hand, a high content of the Ta2O5 component increases costs and leads to a deterioration in devitrification resistance. Therefore, the content of the Ta2O5 component is preferably limited to 3.0% or less, more preferably 2.0% or less, even more preferably 1.0% or less, and even more preferably 0.5% or less. For the Ta2O5 component, Ta2O5 or similar materials can be used as raw materials.

[0031] The Ga2O3 component, when present in amounts greater than 0%, increases the refractive index. On the other hand, a high content of Ga2O3 leads to a deterioration in devitrification resistance. Therefore, the content of the Ga2O3 component is preferably 3.0% or less, more preferably 2.0% or less, even more preferably 1.0% or less, and even more preferably 0.5% or less, and most preferably not present at all. For the Ga2O3 component, Ga2O3 or similar materials can be used as raw materials.

[0032] The SnO2 component is an ingredient that can promote degassing of molten glass. On the other hand, if the SnO2 content is high, the glass becomes more prone to devitrification, and alloying with melting equipment (especially precious metals such as Pt) becomes more likely. Therefore, the SnO2 content is preferably limited to 3.0% or less, more preferably 1.0% or less, even more preferably 0.5% or less, even more preferably 0.3% or less, even more preferably 0.2% or less, and even more preferably 0.1% or less. For the SnO2 component, SnO, SnO2, SnF2, SnF4, etc., can be used as raw materials.

[0033] The Sb2O3 component is an ingredient that can promote degassing of molten glass. On the other hand, if the Sb2O3 content is high, the visible light transmittance tends to decrease, and alloying with melting equipment (especially precious metals such as Pt) is more likely to occur. Therefore, the Sb2O3 content is preferably limited to 2.0% or less, more preferably 1.0% or less, even more preferably 0.5% or less, even more preferably 0.1% or less, and even more preferably 0.09% or less. For the Sb2O3 component, Sb2O3, Sb2O5, Na2H2Sb2O7·5H2O, etc., can be used as raw materials.

[0034] Furthermore, the components used to clarify and degas the glass are not limited to the above-mentioned SnO2 and Sb2O3 components; known clarifying agents, defoaming agents, or combinations thereof used in the field of glass manufacturing can be used.

[0035] Component F is an optional component that, when present in amounts exceeding 0%, can increase the Abbe number of the glass, lower the glass transition temperature, and improve devitrification resistance. However, if the content of component F, that is, the total amount of F in fluorides substituted for some or all of one or more oxides of each of the aforementioned metal elements, exceeds 10.0%, the volatilization rate of component F increases, making it difficult to obtain stable optical constants and homogeneous glass. In addition, the Abbe number rises more than necessary. Therefore, the content of component F may be preferably 10.0% or less, more preferably less than 5.0%, even more preferably less than 3.0%, and even more preferably less than 1.0%.

[0036] Other components may be added as needed, as long as they do not impair the properties of the glass of the present invention. However, each transition metal component, such as V, Cr, Mn, Fe, Co, Ni, Cu, Ag, and Mo (excluding Ti, Zr, Nb, W, La, Gd, Y, Yb, and Lu), has the property of causing the glass to color and producing absorption at specific wavelengths in the visible range, even when present in small amounts, either individually or in combination. Therefore, it is preferable that they be substantially omitted, especially in optical glass used with wavelengths in the visible range.

[0037] Furthermore, lead compounds such as PbO and arsenic compounds such as As2O3 are components with a high environmental impact, so it is desirable that they be substantially omitted, that is, completely omitted except for unavoidable contamination.

[0038] Furthermore, the components Th, Cd, Tl, Os, Be, and Se have recently been increasingly discouraged from use as hazardous chemicals, requiring environmental measures not only in the glass manufacturing process but also in the processing and disposal of the finished product. Therefore, when environmental impact is a major concern, it is preferable to substantially omit these components. (Manufacturing method for optical glass)

[0039] The glass according to the embodiment of the present invention can be produced by blending glass raw materials to have the above-described predetermined composition, and then manufacturing the blended glass raw materials by a known glass manufacturing method. For example, glass raw materials can be blended and mixed to form a batch raw material, and the batch raw material can be placed in a quartz crucible or a platinum crucible to produce cullet. The obtained cullet is blended to achieve the desired refractive index and melted in the melting process. Alternatively, glass raw materials may be blended and mixed to achieve the desired refractive index, and the batch raw materials may be added to the melting process. Water is supplied to the glass during the molding process while increasing the viscosity of the molten glass, and then slow cooling is carried out. Furthermore, the discoloration can be reduced by performing heat treatment on the glass after slow cooling.

[0040] The method of supplying moisture during the molding process is not particularly limited, but examples include providing a moisture supply hole in the mold into which the molten glass is poured during molding, or supplying moisture from there to the molding space. In this case, the shape, size, and number of the supply holes are not particularly limited, but they are preferably round, more preferably square, and the size is an opening diameter of 0.1 to 10 cm. 2 The number should preferably be one or more.

[0041] In addition to supplying moisture from the mold, the moisture content of the atmosphere during the molding process may be increased by means other than supplying moisture from the mold. For example, air with a pre-increased moisture content or an inert gas may be used as the atmosphere for the molding process, or moisture supply means such as nozzles may be provided in the space of the glass molding process.

[0042] Figures 1-3 illustrate specific ways in which moisture is supplied during the molding process. In these figures, arrows indicate the flow of supplied moisture. Figure 1 shows moisture being supplied from a moisture supply port 12 installed inside the molding die 11, Figure 2 shows moisture being supplied from a supply port installed near the molten glass outlet 22 when molten glass is poured into the mold 21, and Figure 3 shows moisture being supplied from a supply port 32 installed above the glass 35 during the glass molding process. To maintain the moisture content in the atmosphere during the molding process within a predetermined range, the molding process can be kept sealed or nearly sealed. For example, the mold itself may be sealed by providing a lid (13 in Figure 1, 23 in Figure 2, and 33 in Figure 3). Alternatively, the entire molding process, or a part of it, may be covered with a chamber isolated from the outside air.

[0043] Regarding the direction in which moisture is supplied to the molding process, there are methods such as supplying it in the same direction as the molding direction, supplying it vertically downwards relative to the glass being molded, or controlling the atmosphere so that the moisture does not directly hit the glass using baffles or other means.

[0044] One method for supplying moisture is to send a predetermined amount of carrier gas and water vapor separately or mixed together to the molding process. While there are no particular limitations on the type of gas, air is the most preferred from a cost perspective, followed by inert gases such as nitrogen, or oxygen. For the carrier gas, it is preferable to use a dry gas to facilitate adjustment of the ratio with water vapor and to stabilize quality.

[0045] The ratio of carrier gas to water vapor, expressed as a supply flow rate ratio, is preferably 80% gas and 20% water vapor, more preferably 60% gas and 40% water vapor, even more preferably 50% gas and 50% water vapor, and even more preferably 30% gas and 70% water vapor. While a water vapor ratio of 100% is also possible, it is preferable to limit the water vapor ratio to 80% to avoid the increased risk of condensation. Water mist, which is equivalent in volume to the gas equivalent, may be used instead of water vapor.

[0046] When using the aforementioned mixed gas, the amount of water supplied during the molding process can reduce discoloration of the glass after slow cooling by supplying the following amounts of water. When the mold volume excluding the glass is 1 L, the supply amount is preferably 0.3 L / min or more, more preferably 1 L / min or more, and even more preferably 2 L / min or more, at 0°C and atmospheric pressure. On the other hand, if the amount of water supplied is too much, the devitrification will worsen, and devitrification will occur on the glass surface due to stimulation of the glass surface. Therefore, it is preferably 30 L / min or less, more preferably 20 L / min or less, and even more preferably 10 L / min or less.

[0047] The method for generating water to supply moisture is not particularly limited and includes vaporizers, bubbling, spraying, and ultrasonic misting, but using a vaporizer is most preferable for stably supplying high-concentration water vapor for a long period of time. The vaporizer may be used only as the water vapor source, or additional vaporizers may be set up near the supply destination for stabilization. The temperature of the vaporizer is not limited, but is preferably 200°C or higher, and more preferably 350°C or higher.

[0048] As a slow cooling process after the molding process, it is preferable to set the rare inlet temperature to 0 to 20°C lower than the glass transition temperature (Tg) in an atmospheric environment, and the holding time is preferably about 1 to 5 hours. After holding at the predetermined temperature, it is preferable to slowly cool to a temperature 300 to 500°C lower than the glass transition temperature (Tg) over a period of 3 to 15 hours.

[0049] Furthermore, to reduce glass discoloration, heat treatment may be performed again after the molding process. The heat treatment conditions are preferably such that the glass, processed into a predetermined shape, is heated from room temperature to a temperature 0 to 20°C below the glass transition temperature (Tg) over 2 to 3 hours, held for 1 to 30 hours, and then cooled at 20 to 30°C / h. This subsequent heat treatment may be repeated multiple times or the holding time may be extended until the discoloration is reduced.

[0050] [Physical properties] (Refractive index and Abbe number) The optical glass of the present invention has a high refractive index while also having a higher dispersion (lower Abbe number). Refractive index (n d The refractive index (n) of the glass of the present invention is preferably 1.75000 or higher. d The refractive index (n) is preferably 1.75000 or higher, more preferably 1.77000 or higher, and even more preferably 1.79000 or higher as the lower limit. d The upper limit of ) may preferably be 2.05000 or less, more preferably 2.03000 or less, and even more preferably 2.01000 or less. Furthermore, the Abbe number (ν) of the glass of the present invention d) is preferably 15.00 or more, more preferably 15.50 or more, and still more preferably 16.00 or more as the lower limit. This Abbe number (ν d ) is preferably 24.0 or less, more preferably 23.5 or less, and still more preferably 23.0 or less as the upper limit.

[0051] (Transmittance after slow cooling) The optical glass of the present invention preferably has particularly reduced coloring after slow cooling. This is because when the coloring after slow cooling is reduced, the time for the next heat treatment becomes shorter. The shortest wavelength (λ 70 ) at which the sample of the glass of the present invention with a thickness of 10 mm after slow cooling shows a spectral transmittance of 70% is preferably 1500 nm or less, more preferably 1450 nm or less, and still more preferably 1400 nm or less as the upper limit.

[0052] (Transmittance after heat treatment) The optical glass of the present invention preferably has a high transmittance of visible light and little coloring after heat treatment. The transmittance of the glass heat-treated after slow cooling is such that the shortest wavelength (λ 70 ) at which the sample of the glass with a thickness of 10 mm shows a spectral transmittance of 70% is preferably 500 nm or less, more preferably 490 nm or less, and still more preferably 480 nm or less.

[0053] (Viscosity) When the viscosity of the glass is η (dPa·s), the viscosity during the molding of the optical glass of the present invention is set to logη 1.5 or less to suppress the occurrence of striae and surface irritation and reduce the coloring during molding. Therefore, it is preferably logη 1.5 or less, more preferably 1.3 or less, and still more preferably logη 1.0 or less.

[0054] (Examples) Regarding the examples (No. 1 to 2) and comparative examples (No. A, B) of the present invention, the differences in the transmittance after slow cooling were compared. The results are shown in Table 1. Also, the refractive index (n d ), Abbe number (ν d ), and transmittance after slow cooling (λ 70), transmittance (λ) after annealing at 660℃ for 2 to 20 hours 70 Table 2 shows the viscosity during molding. Note that the following examples are for illustrative purposes only and the model is not limited to these examples.

[0055] (Batch raw materials) The optical glass of the present invention was prepared by adjusting the raw materials so that the oxide-based composition was P2O5 25.5%, Nb2O5 42.5%, WO 35.4%, TiO2 17.0%, BaO 1.6%, Na2O 4.3%, K2O 3.6%, and Sb2O 30.025%. High-purity raw materials commonly used in optical glass, such as oxides, carbonates, nitrates, fluorides, hydroxides, and metaphosphate compounds, were used as raw materials for each of the above components.

[0056] The prepared batch raw materials were placed in a quartz crucible, melted within a temperature range of 1000-1350°C, and poured into a mold to obtain cullet. Next, the refractive index of the cullet was measured, and the cullet was prepared to achieve the desired refractive index. After melting and homogenizing the mixture within a temperature range of 1000-1350°C for 1-10 hours with stirring, the temperature was lowered to an appropriate level. The material was then manufactured by supplying water during the molding process, pouring it into a mold, and slowly cooling it.

[0057] As a method of supplying moisture, multiple holes of approximately φ4 to φ8 mm were made in the mold used to form the glass (including lids used to maintain an airtight state during the molding process), and moisture was supplied to the molding process through pipes such as copper tubes from these holes. The holes were located inside the molding die (back plate), next to the molten glass outflow nozzle, or during the molding process (lids provided on the mold). The amount of moisture supplied was 2.0 L / min. In Table 2, regarding "direction of moisture supply," "forming direction" means the direction parallel to the direction of movement of the formed glass, and "vertically downward" means the direction perpendicular to the direction of movement of the formed glass. Regarding the "moisture supply location," "back plate" refers to the method of supplying moisture from the back of the mold as shown in Figure 1, "next to the nozzle" refers to the method of supplying moisture from near the molten glass supply nozzle as shown in Figure 2, and "during molding" refers to the method of supplying moisture through a lid or the like installed on the mold during the molding process, as shown in Figure 3.

[0058] After molding, the material was slowly cooled in an air atmosphere at a temperature 0-20°C below the glass transition temperature (Tg) for 1.5 hours, and then slowly cooled to a temperature 380-400°C below the glass transition temperature (Tg) over 4.5 hours.

[0059] Furthermore, heat treatment was performed after slow cooling. The heat treatment conditions were as follows: A separate piece of glass, sized to 50 mm (length) x 50 mm (width) x 20 ± 1 mm (thickness), was heated from room temperature to 0-20°C below the glass transition temperature (Tg) over 2-3 hours, held for 1-30 hours, and then cooled to 200-220°C below the glass transition temperature (Tg) at a rate of 25°C / h. Subsequently, the material was cut out with a central section measuring 15-30 mm vertically and 15-30 mm horizontally, and an end section measuring 15-30 mm vertically and 0-15 mm horizontally. The transmittance was measured using the above processing dimensions and measurement method, and the heat treatment holding time was extended or repeated until the difference between the central and end sections was 5 nm or less at the wavelength (λ70) where the spectral transmittance was 70%.

[0060] (Refractive index and Abbe number) Refractive index (n) of the glass in the examples and comparative examples. d ), Abbe number (ν d The refractive index (n) was measured in accordance with the V-block method specified in JIS B 7071-2:2018. d The values ​​shown are measured values ​​for the d-line (587.56 nm) of a helium lamp. Also, the Abbe number (ν) d ) is the refractive index (n) of a helium lamp with respect to the d line. d ) and the refractive index (n) of the hydrogen lamp relative to the F line (486.13 nm). F ), refractive index (n) for the C line (656.27 nm) C Using the value of ), the Abbe number (νd )=[(n d -1) / (n F -n C These refractive indices (n d ), Abbe number (ν d The temperature was determined by measuring the temperature of glass obtained by slow cooling at a rate of -25°C / hr.

[0061] (transmittance) The transmittance of the glass in the examples and comparative examples was measured in accordance with the Nippon Optical Glass Manufacturers Association standard (JOGIS02-2019 Method for measuring the degree of coloration of optical glass). In this invention, the presence and degree of coloration of the glass were determined by measuring the transmittance of the glass. Specifically, the spectral transmittance of a face-to-face parallel polished product with a thickness of 10 ± 0.1 mm was measured in accordance with JIS Z 8722, and the λ after slow cooling was measured. 70 (Wavelength at 70% transmittance), λ after heat treatment 70 The wavelength at a transmittance of 70% was determined.

[0062] (viscosity) The viscosity of the optical glass during molding for Examples 1-5 and Comparative Examples A-C was measured using a ball-draw type viscometer (model BVM-13LH, manufactured by Opto Enterprise Co., Ltd.) with a measurement temperature range from the melting process temperature to the molding temperature (or 1000-1400°C), and viscosity η (dPa·s) was measured. The viscosity at the molding temperature was calculated by taking the logarithm of the measured viscosity η. The molding temperature referred to here is the temperature of the pipe during outflow as shown in Figures 14, 24, and 34, and is 1130°C for Examples 1-5 and Comparative Examples A-C.

[0063] [Table 1]

[0064] [Table 2]

[0065] As shown in Table 1, the optical glasses of Examples 1 and 2, manufactured using the manufacturing method of the present invention, showed a spectral transmittance of 70% after slow cooling at a wavelength (λ70) of 1290 nm or less, achieved by supplying water during the molding process.

[0066] Furthermore, as shown in Table 2, the optical glass of Examples 3 to 5 all have a refractive index (n d The Abbe number (ν) was 1.95000 or higher, which was within the desired range. Furthermore, all of the optical glasses in the embodiments of the present invention had an Abbe number (ν). d The value was within the range of 15.00 to 24.00, which was within the desired range. Furthermore, the transmittance after heat treatment was also found to be good. In addition, the heat treatment time was improved by 2 to 4 hours.

[0067] Furthermore, using the optical glass of the embodiment of the present invention, glass blocks were formed, and these glass blocks were ground and polished to process them into the shapes of lenses and prisms. As a result, it was possible to stably process them into various lens and prism shapes.

[0068] Although the present invention has been described in detail above for illustrative purposes, it will be understood that these embodiments are for illustrative purposes only, and that many modifications can be made by those skilled in the art without departing from the spirit and scope of the present invention. [Brief explanation of the drawing]

[0069] [Figure 1] This is a schematic diagram showing an example of a molding apparatus used in carrying out the molding method according to the present invention. [Figure 2] This is a schematic diagram showing an example of a molding apparatus used in carrying out the molding method according to the present invention. [Figure 3] This is a schematic diagram showing an example of a molding apparatus used in carrying out the molding method according to the present invention. [Explanation of Symbols]

[0070] 11. Forming mold (die) 12 Moisture supply hole 13. Lid (ceiling panel) 14. Molten glass outlet nozzle 15. Molten glass 21. Forming mold (die) 22 Moisture supply hole 23 Lid (ceiling panel) 24 Molten glass outlet nozzle 25 molten glass 31. Forming mold (die) 32 Moisture supply hole 33 Lid (ceiling panel) 34. Molten glass discharge nozzle 35 molten glass

Claims

[Claim 1] In mass % of the total mass of glass in terms of oxide, P2O5 at 15-40%, TiO2 is greater than 0% to 30%. Nb₂O₅ at 35.0-60% Contains, WO 3 is below 20%, A method for manufacturing optical glass having a refractive index (n d) of 1.79000 or more, The blending process involves mixing the raw materials, The melting process involves melting the raw materials to produce molten glass, A molding process that increases the viscosity of molten glass while shaping it. Includes, The molding process is characterized by supplying water to the glass, A method for manufacturing optical glass.

Images