Optical glass and optical element

Abstract

To provide optical glass and an optical element, each of which has high internal transmittance and high refractive index at a wavelength of 460 nm.SOLUTION: The present invention relates to an optical glass, wherein: a mass ratio [(BaO+La2O3+Gd2O3+WO3) / (CaO+SrO+Y2O3)] of a total amount of BaO, La2O3, Gd2O3, and WO3 contained to the total amount of CaO, SrO, and Y2O3 contained is 2.0 or less; a mass ratio [(B2O3+P2O5) / (SiO2+Al2O3)] of a total amount of B2O3 and P2O5 contained to a total amount of SiO2 and Al2O3 contained is 0.10 or less; a total amount [Li2O+Na2O+K2O] of Li2O, Na2O, and K2O contained is 10 mass% or less; and a mass ratio [(Al2O3 / (SiO2+ZrO2)] of the amount of Al2O3 contained to the total amount of SiO2 and ZrO2 contained is greater than 0.0000.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to an optical glass and an optical element. [Background technology]

[0002] In recent years, with the advancement of AR (Augmented Reality) technology, goggle-type or eyeglass-type display devices have been developed as AR devices. For example, goggle-type display devices use flat lenses with high refractive index, high transmittance, and low specific gravity, and there is an increasing demand for glass that can be used for such lenses. The transmittance here refers to the internal transmittance when light passes through the inside of the glass, and is distinguished from the external transmittance that includes reflection losses.

[0003] In general, the refractive index of glass increases as the interaction between the light passing through the glass and the electron cloud in the glass increases. Therefore, to increase the refractive index of glass, glass components are selected so that more electrons are filled in the glass. In other words, glass components with a large atomic number relative to their ionic radius and containing many electrons are selected to increase the electron density (usually the oxygen number density) per unit volume of the glass. Lanthanum borate-based glass is one example. However, lanthanum borate-based glass has a high specific gravity, and when used in goggle-type AR display devices, the lenses become heavy, which is a problem.

[0004] Glass components that can increase the refractive index while maintaining a low specific gravity include Nb2O5 and TiO2, which have absorption in the near ultraviolet region. However, when the content of such glass components increases, there is a problem that the light absorption region expands not only to the near ultraviolet region but also to the visible short wavelength region (blue region). In addition, when the content of Nb2O5 or TiO2 increases, the proportion of other ions that can donate oxygen to Nb ions and Ti ions relatively decreases, so some of the Nb ions and Ti ions are reduced and colored, and there is a problem that the internal transmittance of the glass in visible light decreases.

[0005] Another factor that reduces the transmittance of glass is the inclusion of platinum (Pt) from the glass melting furnace. For example, if the content of Nb2O5, TiO2, etc. is increased in an attempt to increase the refractive index of glass, the melting temperature of the glass rises, and the glass raw materials must be heated at high temperatures. At this time, when the high-temperature molten glass comes into contact with platinum (Pt), the Pt ions dissolve into the molten glass and form a solid solution in the glass. Pt has absorption in the ultraviolet range, but if the amount of Pt in the glass increases, the light absorption range expands not only to the ultraviolet range but also to the visible light range. As a result, the internal transmittance of the glass in the visible light range decreases.

[0006] On the other hand, in the case of glass that can be melted in a furnace using refractory bricks, the inclusion of platinum (Pt) originating from the furnace is suppressed. As an example of glass that can be melted in a furnace using refractory bricks, there is SiO2-TiO2-based glass. It is known that the refractive index nd of this type of glass can be increased to about 1.85, the specific gravity can be reduced to about 3.5, and the transmittance is relatively excellent (Patent Document 1).

[0007] Here, refractory bricks are bricks whose main components are ZrO2, Al2O3 and / or SiO2 (see, for example, Patent Document 2). The content ratio of each component is, for example, ZrO2:Al2O3:SiO2 = 4:5:1 or about 3:6:1, but as shown in, for example, https: / / www.an.shimadzu.co.jp / apl / material / chem0502005.htm, there are also refractory bricks that contain almost no Al2O3 or SiO2. However, as shown in Patent Document 2, a certain amount of Al2O3 is often contained to improve thermal shock resistance and corrosion resistance.

[0008] However, in order to apply it to lenses for AR display devices, the refractive index needs to be further increased. For example, Patent Document 3 discloses SiO2-TiO2-based glass having a refractive index nd in the range of 1.86 to 1.99 and an Abbe number νd in the range of 21 to 29. However, this glass has a high melting temperature and corrodes the glassy part of the refractory bricks of the melting furnace, which results in a problem that the components of the refractory bricks are easily mixed into the glass. If a large amount of components derived from the refractory bricks, particularly ZrO2 components and SiO2 components, are dissolved in the glass, the glass composition changes, making it difficult to maintain the stability of the glass or maintain a high refractive index. In addition, crystalline components such as Al2O3 and ZrO2, which are the main components of the refractory bricks, are mixed into the glass as foreign matter, which impairs the homogeneity of the glass. For this reason, such glasses are melted in platinum containers, but when glass is melted in a platinum container, Pt is introduced into the glass as described above, which causes a problem of reduced internal transmittance.

[0009] If the glass is a SiO2-based glass containing Nb2O5, TiO2, etc. and can be melted in a furnace using refractory bricks, it is possible to improve the transmittance while maintaining a high refractive index. Such glass is useful for lenses in AR display devices. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Patent No. 2535407 [Patent Document 2] Special Publication No. 2018-537387 [Patent Document 3] JP 2012-229135 A Summary of the Invention [Problem to be solved by the invention]

[0011] The present invention has been made in view of the above circumstances, and has an object to provide an optical glass and an optical element having a high internal transmittance at a wavelength of 460 nm and a high refractive index. [Means for solving the problem]

[0012] The gist of the present invention is as follows. (1) the mass ratio of the total content of BaO, La2O3, Gd2O3, and WO3 to the total content of CaO, SrO, and Y2O3 [(BaO+La2O3+Gd2O3+WO3) / (CaO+SrO+Y2O3)] is 2.0 or less; the mass ratio of the total content of B2O3 and P2O5 to the total content of SiO2 and Al2O3 [(B2O3+P2O5) / (SiO2+Al2O3)] is 0.10 or less; The total content of LiO, NaO, and KO [LiO + NaO + KO] is 10 mass% or less, An optical glass having a mass ratio of the Al2O3 content to the total SiO2 and ZrO2 content [(Al2O3 / (SiO2+ZrO2)]] greater than 0.0000.

[0013] (2) The total content of TiO2 and Nb2O5 [TiO2 + Nb2O5] is 20 mass% or more, An optical glass having a mass ratio of the Al2O3 content to the total SiO2 and ZrO2 content [(Al2O3 / (SiO2+ZrO2)]] greater than 0.0000.

[0014] (3) The optical glass according to (2), in which the mass ratio of the total content of B2O3 and P2O5 to the total content of SiO2 and Al2O3 [(B2O3+P2O5) / (SiO2+Al2O3)] is 0.15 or less.

[0015] (4) The total content of TiO2, Nb2O5, and ZrO2 and the ratio of B2O3, SiO2, and Al The mass ratio of the total content of TiO2, Nb2O5, ZrO2, and GeO2 [(TiO2+Nb2O5+ZrO2) / (B2O3+SiO2+Al2O3+GeO2)] is 1.8 or more, The optical glass according to (2) or (3), in which the mass ratio of the total content of BaO, La2O3, Gd2O3, and WO3 to the total content of CaO, SrO, and Y2O3 [(BaO+La2O3+Gd2O3+WO3) / (CaO+SrO+Y2O3) is 3.0 or less.

[0016] (5) the mass ratio of the total content of TiO2, Nb2O5, and ZrO2 to the total content of B2O3, SiO2, Al2O3, and GeO2 [(TiO2+Nb2O5+ZrO2) / (B2O3+SiO2+Al2O3+GeO2)] is 1.8 or more; The optical glass according to any one of (2) to (4), in which the mass ratio of the total content of B2O3, ZnO, La2O3, Gd2O3, and WO3 to the total content of SiO2, CaO, TiO2, and Nb2O5 [(B2O3+ZnO+La2O3+Gd2O3+WO3) / (SiO2+CaO+TiO2+Nb2O5)] is 0.15 or less.

[0017] (6) An optical element made of the optical glass according to any one of (1) to (5) above. Effect of the Invention

[0018] According to the present invention, it is possible to provide an optical glass and an optical element having a high internal transmittance at a wavelength of 460 nm and a high refractive index. [Brief description of the drawings]

[0019] [Figure 1] 1 is a graph showing the internal transmittance in an example of an optical glass according to an embodiment of the present invention, showing λτ90, which is the wavelength at which the internal transmittance becomes 90%. [Diagram 2] 6 is a photograph showing the results of an erosion test of a brick sample in Example 2. [Diagram 3] FIG. 1 shows the positions at which the diameter of a brick sample was measured in the erosion test of Example 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] Hereinafter, one embodiment of the present invention will be described. In the present invention and this specification, the glass composition is expressed on an oxide basis unless otherwise specified. Here, "glass composition on an oxide basis" refers to a glass composition obtained by converting the glass raw materials into oxides that are all decomposed during melting and exist in the glass, and each glass component is conventionally expressed as SiO2, TiO2, etc. The content and total content of the glass components are on a mass basis unless otherwise specified, and "%" means "mass%".

[0021] The content of the glass component can be quantified by known methods, such as inductively coupled plasma atomic emission spectrometry (ICP-AES), inductively coupled plasma mass spectrometry (ICP-MS), etc. In this specification and the present invention, the content of a component being 0% means that the component is substantially not contained, and it is acceptable for the component to be contained at an unavoidable impurity level.

[0022] The optical glass of the present invention will be described below in two separate embodiments: a first embodiment and a second embodiment. The actions and effects of each glass component in the second embodiment are the same as those of the first embodiment. Therefore, in the second embodiment, matters that overlap with the description of the first embodiment will be omitted as appropriate.

[0023] First embodiment The optical glass according to the first embodiment of the present invention is The total contents of BaO, La2O3, Gd2O3, and WO3 and CaO, SrO, and and the mass ratio of the total content of BaO+La2O3+Gd2O3+WO3) / (CaO+SrO+Y2O3)] is 2.0 or less, the mass ratio of the total content of B2O3 and P2O5 to the total content of SiO2 and Al2O3 [(B2O3+P2O5) / (SiO2+Al2O3)] is 0.10 or less; The total content of Li2O, Na2O, and K2O [Li2O + Na2O + K2O] is 10% or less, The mass ratio of the Al2O3 content to the total content of SiO2 and ZrO2 [(Al2O3 / (SiO2+ZrO2)]] is greater than 0.0000.

[0024] In the optical glass according to the first embodiment, the mass ratio of the total content of BaO, La2O3, Gd2O3, and WO3 to the total content of CaO, SrO, and Y2O3 [(BaO+La2O3+Gd2O3+WO3) / (CaO+SrO+Y2O3)] is 2.0 or less. The upper limit of this mass ratio is preferably 1.9, and more preferably 1.8, 1.7, and 1.6 in that order. The lower limit of this mass ratio is preferably 0.0, and more preferably 0.3, 0.5, 0.8, 1.0, and 1.2 in that order.

[0025] By setting the mass ratio [(BaO+La2O3+Gd2O3+WO3) / (CaO+SrO+Y2O3)] in the above range, it is possible to suppress the content of high refractive index components with too large atomic weights, particularly elements from the 6th period onwards that act to relatively increase the refractive index, or to limit the amount of high refractive index components that promote oxygen filling, thereby reducing the specific gravity of the glass. On the other hand, if the mass ratio is too large, the specific gravity of the glass increases, decreasing the kinetic viscosity of the molten glass, making it difficult to control the glass flow, and there is a risk of productivity deteriorating. There is also a risk of increased erosion of the refractory bricks.

[0026] In the optical glass according to the first embodiment, the mass ratio of the total content of B2O3 and P2O5 to the total content of SiO2 and Al2O3 [(B2O3+P2O5) / (SiO2+Al2O3)] is 0.10 or less. The upper limit of this mass ratio is preferably 0.09, more preferably 0.08, 0.07, and 0.06 in that order. The lower limit of this mass ratio is preferably 0.00, more preferably 0.01, 0.02, 0.03, 0.04, and 0.05 in that order.

[0027] By setting the mass ratio [(B2O3+P2O5) / (SiO2+Al2O3)] in the above range, it is possible to suppress erosion of the vitreous matter of the refractory bricks during glass melting. If the mass ratio is too large, the erosion of the refractory bricks becomes significant, which may reduce the homogeneity of the molten glass and decrease the devitrification resistance.

[0028] In the optical glass according to the first embodiment, the total content of Li2O, Na2O, and K2O [Li2O+Na2O+K2O] is 10% or less. The upper limit of the total content is preferably 8.0%, more preferably 6.0%, 5.0%, and 4.0%, in that order. The lower limit of the total content is preferably 0.01%, more preferably 0.5%, 1.0%, 1.5%, 2.0%, and 3.0%, in that order.

[0029] By setting the total content [Li2O+Na2O+K2O] within the above range, the viscosity of the glass can be appropriately maintained and the productivity of the glass can be improved. In addition, the light absorption caused by the reducing components generated by Ti and Nb can be suppressed, and further, the melting temperature can be lowered and the elimination of electronic defects in the glass due to slow cooling can be promoted, thereby increasing the internal transmittance at 460 nm. In addition, the erosion of the refractory brick during glass melting can be suppressed. On the other hand, if the total content is too small, the melting property of the glass raw material is deteriorated, and it becomes necessary to set the melting temperature of the raw material higher. As a result, the deterioration of the refractory brick is promoted, and the productivity is deteriorated. On the other hand, if the total content is too large, the viscosity of the glass decreases and the thermal stability is decreased accordingly, which may deteriorate the productivity. In addition, the resistivity of the molten glass decreases, which reduces the heating efficiency when the molten glass is heated by passing electricity, which may result in a deterioration of the melting property of the glass and a deterioration of the productivity.

[0030] In the optical glass according to the first embodiment, the mass ratio of the Al2O3 content to the total content of SiO2 and ZrO2 [(Al2O3 / (SiO2+ZrO2)]] is greater than 0.0000. The lower limit of this mass ratio is preferably 0.0001, and more preferably 0.0003, 0.0006, 0.0010, 0.0020, 0.0030, 0.0040, 0.0050, and 0.0060, in that order. The upper limit of this mass ratio is preferably 0.3000, and more preferably 0.2000, 0.1500, 0.1000, 0.0500, 0.0300, and 0.0150, in that order.

[0031] By setting the mass ratio [(Al2O3 / (SiO2+ZrO2)] within the above range, it is possible to suppress erosion of the refractory bricks during glass melting. Furthermore, compared with glasses having a ratio outside the above range, this has the effect of increasing thermal stability and delaying devitrification during heating or crystal precipitation when the molten glass is cooled. On the other hand, if the mass ratio is too large, not only does the refractive index nd decrease, but the thermal stability also decreases, and there is a risk of devitrification.

[0032] Hereinafter, preferred aspects of the optical glass according to the first embodiment will be described.

[0033] In the optical glass according to the first embodiment, the lower limit of the total content of TiO2 and Nb2O5 [TiO2+Nb2O5] is preferably 20%, more preferably 24%, 28%, 33%, 37%, 40%, and 42%, in that order. The upper limit of the total content is preferably 70%, more preferably 60%, 55%, 50%, and 46%, in that order.

[0034] TiO2 and Nb2O5 are components that contribute to a high refractive index without increasing the specific gravity too much. Therefore, in order to obtain a glass having a desired refractive index without increasing the specific gravity of the glass too much, it is preferable that the total content of TiO2 and Nb2O5 is within the above range.

[0035] In the optical glass according to the first embodiment, the lower limit of the mass ratio of the total content of TiO2, Nb2O5, and ZrO2 to the total content of B2O3, SiO2, Al2O3, and GeO2 [(TiO2+Nb2O5+ZrO2) / (B2O3+SiO2+Al2O3+GeO2)] is preferably 1.8, more preferably 2.0, 2.1, 2.2, and 2.3 in that order. The upper limit of the mass ratio is preferably 7.0, more preferably 6.0, 5.0, 4.0, 3.5, and 3.0 in that order.

[0036] By setting the mass ratio [(TiO2+Nb2O5+ZrO2) / (B2O3+SiO2+Al2O3+GeO2)] in the above range, the refractive index is increased, and a wide viewing angle can be achieved when used as a lens for a display device of an AR device. In addition, an optical glass with a further reduced specific gravity is obtained. On the other hand, if the mass ratio is too small, the refractive index relative to the specific gravity is reduced, which is not suitable for the application of the present invention. Also, if the mass ratio is too large, the stability of the glass is reduced and the transmittance may be reduced.

[0037] In the optical glass according to the first embodiment, the upper limit of the total content of B2O3, ZnO, La2O3, Gd2O3, and WO3 and the total content of SiO2, CaO, TiO2, and Nb2O5 and the mass ratio [(B2O3+ZnO+La2O3+Gd2O3+WO3) / (SiO2+CaO+TiO2+Nb2O5)] is preferably 0.15, more preferably 0.12, 0.10, and 0.08 in that order. The lower limit of the mass ratio is preferably 0.01, more preferably 0.02, 0.03, 0.04, 0.05, and 0.06 in that order.

[0038] By setting the mass ratio [(B2O3+ZnO+La2O3+Gd2O3+WO3) / (SiO2+CaO+TiO2+Nb2O5)] in the above range, the content of glass components that are usually contained in large amounts in glasses that use boric acid as a network former can be reduced, and as a result, the erosion of refractory bricks during glass melting can be suppressed. As a result, the contact between the glass and platinum can be suppressed, and the internal transmittance of the glass can be increased. In addition, by setting the mass ratio in the above range, the amount of components with too large atomic weights or components with high refractive index that promote oxygen filling can be limited, so that the specific gravity can be lowered even with the same refractive index, and the productivity can be improved by suppressing the decrease in the kinetic viscosity of the glass.

[0039] In the optical glass according to the first embodiment, the lower limit of the Al2O3 content is preferably 0.001%, and more preferably 0.002%, 0.003%, 0.005%, 0.007%, 0.010%, 0.025%, 0.050%, 0.075%, 0.100%, 0.125%, 0.150%, 0.175%, and 0.200%, in that order. The upper limit of the Al2O3 content is preferably 10.0%, and more preferably 6.0%, 3.0%, 1.00%, and 0.50%, in that order.

[0040] When glass is melted in a furnace using refractory bricks, Al2O3 derived from the refractory bricks is introduced into the molten glass. Therefore, even if the glass raw material does not contain Al2O3, a small amount of Al2O3 is contained in the glass produced by melting in a furnace using refractory bricks. When the content of Al2O3 is within the above range, the thermal stability is high, devitrification during heating is suppressed, and crystal precipitation during cooling of the molten glass is suppressed, compared with the case where the content of Al2O3 is outside the above range. However, since Al2O3 is a component that has a small effect of reducing the specific gravity and a function of reducing the refractive index, the lower the content of Al2O3, the more preferable it is from the viewpoint of obtaining a glass with a high refractive index and low specific gravity. In addition, if the content of Al2O3 is too high, the devitrification resistance of the glass decreases, the glass transition temperature Tg increases, and the thermal stability may decrease. On the other hand, if the Al2O3 content is too low, there is a risk of increased erosion of the refractory bricks.

[0041] Non-limiting examples of the contents and ratios of glass components other than those described above in the optical glass according to the first embodiment are given below.

[0042] In the optical glass according to the first embodiment, the lower limit of the mass ratio [(TiO2+CaO+SrO+Y2O3) / (BaO+MgO+Nb2O5+Ta2O5+WO3+Bi2O3+La2O3+Gd2O3)] of the total content of TiO2, CaO, SrO, and Y2O3 to the total content of BaO, MgO, Nb2O5, Ta2O5, WO3, Bi2O3, La2O3, and Gd2O3 is preferably 0.5, more preferably 0.6, 0.7, 0.8, 0.9, and 1.0 in that order. The upper limit of the mass ratio is preferably 4.0, more preferably 3.0, 2.5, 2.0, and 1.5 in that order.

[0043] By setting the mass ratio [(TiO2+CaO+SrO+Y2O3) / (BaO+MgO+Nb2O5+Ta2O5+WO3+Bi2O3+La2O3+Gd2O3)] in the above range, an optical glass with a high refractive index nd and a low specific gravity can be obtained. If the mass ratio is too small, it may be difficult to achieve both a high refractive index and a low specific gravity. If the mass ratio is too large, the stability of the glass may decrease.

[0044] In the optical glass according to the first embodiment, the lower limit of the mass ratio [TiO2 / Nb2O5] of the TiO2 content to the Nb2O5 content is preferably 0.5, and more preferably 0.53, 0.54, 0.55, 0.6, 0.7, 0.8, 0.9, and 1.0 in that order. The upper limit of the mass ratio [TiO2 / Nb2O5] is preferably 4.0, and more preferably 3.0, 2.5, 2.0, and 1.5 in that order.

[0045] By setting the mass ratio [TiO2 / Nb2O5] within the above range, the stability of the glass can be improved while reducing the specific gravity of the glass. On the other hand, if the mass ratio is too small, the liquidus temperature increases, the melting property deteriorates, and the erosion of the refractory brick during glass melting may increase. In addition, the manufacturing cost may increase. On the other hand, if the mass ratio is too large, the devitrification resistance of the glass may decrease, and the transmittance of the glass may decrease.

[0046] In the optical glass according to the first embodiment, the lower limit of the total content of MgO, CaO, SrO, and BaO [MgO+CaO+SrO+BaO] is preferably 5.0%, more preferably 10.0%, 15.0%, 18.0%, 22.0%, and 25.0%, in that order. The upper limit of the total content is preferably 50.0%, more preferably 45.0%, 40.0%, 36.0%, 33.0%, and 30.0%, in that order.

[0047] By setting the total content [MgO+CaO+SrO+BaO] within the above range, the meltability of the glass can be improved and the thermal stability of the glass can be increased. On the other hand, if the total content is too small, the meltability of the glass may be deteriorated and the erosion of the refractory brick during glass melting may be increased. Also, if the total content is too large, the desired optical properties may not be obtained and the stability may be reduced.

[0048] In the optical glass according to the first embodiment, the lower limit of the mass ratio [(Li2O+Na2O+K2O) / (MgO+CaO+SrO+BaO)] of the total content of Li2O, Na2O, and K2O to the total content of MgO, CaO, SrO, and BaO is preferably 0.00020, and more preferably 0.001, 0.005, 0.010, 0.050, and 0.100 in that order. The upper limit of the mass ratio is preferably 2.0, and more preferably 1.5, 1.0, 0.5, 0.3, and 0.2 in that order.

[0049] By setting the mass ratio [(Li2O+Na2O+K2O) / (MgO+CaO+SrO+BaO)] in the above range, the specific gravity of the glass is easily reduced. In addition, by suppressing the reduction of the glass, the internal transmittance is easily increased. On the other hand, if the mass ratio is too small, the meltability of the glass may deteriorate, and the erosion of the refractory brick during glass melting may increase. In addition, if the mass ratio is too large, the homogeneity of the glass may decrease due to the volatilization and striae of the glass components, and the stability may decrease due to a decrease in viscosity.

[0050] In the optical glass according to the first embodiment, the lower limit of the ratio [(Li2O / 29.9) / {(B2O3 / 69.6+Li2O / 29.9+Na2O / 62.0+K2O / 94.2)}] of the value obtained by dividing the content of Li2O by 29.9, the value obtained by dividing the content of B2O3 by 69.6, the value obtained by dividing the content of Li2O by 29.9, the value obtained by dividing the content of Na2O by 62.0, and the value obtained by dividing the content of K2O by 94.2 is preferably 0.10, and more preferably 0.20, 0.30, 0.40, 0.45, and 0.50 in that order. The upper limit of the ratio is preferably 1.00, and more preferably 0.90, 0.80, 0.70, 0.60, and 0.55 in that order. Here, the divisor of the content of each glass component corresponds to the molecular weight of each oxide, so this ratio roughly represents the proportion of the number of Li ions to the total number of Li ions, B ions, Na ions, and K ions in the glass.

[0051] By setting the ratio [(Li2O / 29.9) / (B2O3 / 69.6+Li2O / 29.9+Na2O / 62.0+K2O / 94.2)] in the above range, the glass can be densely packed, and a glass with a low specific gravity and a high refractive index can be obtained without introducing a high-melting point, high-refractive index component that would increase the melting temperature of the glass. Furthermore, as a result of the increase in the number of Li ions, the heating efficiency when heating the molten glass by applying electricity is improved, and the fluidity of the molten glass can also be increased. In addition, by setting this ratio in the above range, it is possible to ensure the meltability of the glass, while suppressing reduction coloring that may occur during melting of the glass and increasing the internal transmittance. On the other hand, if the ratio is too small, the resistivity of the molten glass increases, and a higher voltage must be applied during electric melting, which may result in increased erosion of the refractory bricks during glass melting. On the other hand, if the ratio is too large, the stability of the glass may decrease.

[0052] In the optical glass according to the first embodiment, the lower limit of the SiO2 content is preferably 5.0%, more preferably 8.0%, 11.0%, 13.0%, and 15.0%, in that order. The upper limit of the SiO2 content is preferably 35.0%, more preferably 30.0%, 27.0%, 25.0%, 23.0%, and 21.0%, in that order.

[0053] SiO2 is a glass network forming component that improves the thermal stability, chemical durability, and weather resistance of glass, and also works to increase the viscosity of molten glass. If the SiO2 content is too low, the devitrification resistance of glass tends to decrease. If the SiO2 content is too high, the refractive index nd decreases, the viscosity increases, and the partial dispersion ratio Pg,F may increase.

[0054] In the optical glass according to the first embodiment, the lower limit of the ZrO2 content is preferably 0.0000%, and more preferably 0.0005%, 0.0010%, 0.0050%, 0.0100%, 0.0500%, 0.1%, 0.5%, 1.0%, and 1.5%, in that order. The upper limit of the ZrO2 content is preferably 15.0%, and more preferably 10.0%, 7.0%, 5.0%, 3.0%, and 2.0%, in that order.

[0055] When glass is melted in a furnace using refractory bricks, ZrO2 derived from the refractory bricks tends to be introduced into the molten glass. Therefore, if the glass raw material does not contain ZrO2, the glass produced by melting in a furnace using refractory bricks may contain a small amount of ZrO2. In addition, Zr may be supplied to the glass by contact between the strengthening platinum and the glass melt. If the content of ZrO2 is too low, the erosion of the refractory bricks may increase. If the content of ZrO2 is too high, the meltability of the glass may deteriorate. By setting the content of ZrO2 within the above range, it is possible to obtain glass with a high refractive index while suppressing the erosion of the bricks. In addition, the meltability and thermal stability of the glass can be maintained.

[0056] In the optical glass according to the first embodiment, the upper limit of the P2O5 content is preferably 5.0%, and more preferably 4.0%, 3.0%, 2.0%, 1.0%, and 0.6%, in that order. The lower the P2O5 content, the more preferable it is, and the lower limit is preferably 0.0%, but it may be incorporated in a range of 0.20% or more, 0.40% or more to adjust the stability and liquidus temperature of the glass. The P2O5 content may be 0.0%.

[0057] By setting the content of P2O5 within the above range, devitrification of the glass can be suppressed, and erosion of the refractory bricks during glass melting can be suppressed.

[0058] In the optical glass according to the first embodiment, the upper limit of the B2O3 content is preferably 15.0%, and more preferably 10.0%, 6.0%, 3.0%, 2.0%, and 1.0%, in that order. The lower limit of the B2O3 content is preferably 0.0%, and more preferably 0.1%, 0.2%, 0.4%, and 0.7%, in that order.

[0059] B2O3 has the function of improving the thermal stability of glass and enhancing the meltability of glass. In addition, among the components that form the glass network, it is a component that has a relatively high refractive index and can reduce the specific gravity. By setting the content of B2O3 within the above range, the meltability of glass is improved and an optical glass with a high refractive index and a reduced specific gravity is obtained. On the other hand, if the content of B2O3 is too small, the high refractive index may be lost and the specific gravity may increase. In addition, if the content of B2O3 is too large, the amount of volatilization of glass components during glass melting may increase. In addition, it tends to hinder high dispersion and reduce devitrification resistance.

[0060] In the optical glass according to the first embodiment, the lower limit of the total content of SiO2 and Al2O3 [SiO2+Al2O3] is preferably 5%, more preferably 8%, 11%, and 13%, in that order. The upper limit of the total content [SiO2+Al2O3] is preferably 40%, more preferably 35%, 30%, 25%, 23%, 21%, and 15%, in that order.

[0061] By setting the total content [SiO2+Al2O3] within the above range, it is possible to suppress the erosion of the refractory brick during glass melting. However, if the total content is too large, the specific gravity does not decrease much, but the refractive index decreases significantly, and there is a risk that the desired refractive index of the present invention cannot be obtained.

[0062] In the optical glass according to the first embodiment, the lower limit of the total content of B2O3 and P2O5 [B2O3+P2O5] is preferably 0.1%, more preferably 0.2%, 0.4%, 0.7%, and 1%, in that order. The upper limit of the total content [B2O3+P2O5] is preferably 10%, more preferably 6%, 3%, and 2%, in that order.

[0063] By setting the total content [B2O3+P2O5] within the above range, the viscosity of the glass can be maintained to increase the stability, and erosion of refractory bricks during glass melting can be suppressed.

[0064] In the optical glass according to the first embodiment, the lower limit of the TiO2 content is preferably 5.0%, and more preferably 10.0%, 14.0%, 14.2%, 14.5%, 14.8%, 15.0%, 18.0%, and 20.0%, in that order. The upper limit of the TiO2 content is preferably 40.0%, and more preferably 35.0%, 30.0%, 25.0%, and 22.0%, in that order.

[0065] By setting the TiO2 content within the above range, a glass with a high refractive index and a low specific gravity can be obtained. It also has the effect of reducing the ultraviolet transmittance. On the other hand, if the TiO2 content is too low, the refractive index may decrease and the specific gravity may increase. Also, if the TiO2 content is too high, the internal transmittance of the glass in the visible range, especially in the short wavelength range, may decrease, and the devitrification resistance may also decrease.

[0066] In the optical glass according to the first embodiment, the lower limit of the Nb2O5 content is preferably 0.0%, and more preferably 5.0%, 10.0%, 13.0%, and 15.0%, in that order. The upper limit of the Nb2O5 content is preferably 40.0%, and more preferably 35.0%, 30.0%, 28.0%, 27.0%, 26.0%, 25.0%, 20.0%, and 17.0%, in that order.

[0067] By setting the content of Nb2O5 within the above range, an optical glass having a high refractive index and a relatively low specific gravity can be obtained. On the other hand, if the content of Nb2O5 is too low, the refractive index may decrease and the specific gravity may increase. If the content of Nb2O5 is too high, the devitrification resistance may decrease.

[0068] In the optical glass according to the first embodiment, the lower limit of the total content of TiO2, Nb2O5, and ZrO2 [TiO2+Nb2O5+ZrO2] is preferably 25%, more preferably 30%, 35%, 40%, and 45%, in that order. The upper limit of the total content is preferably 75%, more preferably 70%, 60%, 55%, 52.5%, and 50%, in that order.

[0069] By setting the total content [TiO2 + Nb2O5 + ZrO2] within the above range, an optical glass having a high refractive index and high internal transmittance at a specified wavelength can be obtained while suppressing an increase in specific gravity.

[0070] In the optical glass according to the first embodiment, the upper limit of the WO3 content is 5.0%, and more preferably 3.0%, 2.0%, 1.0%, and 0.5%, in that order. The lower limit of the WO3 content is preferably 0.0%. The WO3 content may be 0.0%.

[0071] By setting the content of WO3 within the above range, the specific gravity is reduced, and an optical glass with reduced ultraviolet transmittance is obtained. On the other hand, if the content of WO3 is too high, the partial dispersion ratio Pg,F increases, the internal transmittance decreases, and the specific gravity increases. In addition, the transmittance in the visible range, especially in the short wavelength range, decreases, and the glass may become unstable.

[0072] In the optical glass according to the first embodiment, the upper limit of the Bi2O3 content is 5.0%, and more preferably 3.0%, 2.0%, 1.0%, and 0.5%, in that order. The lower limit of the Bi2O3 content is preferably 0.0%. The Bi2O3 content may be 0.0%.

[0073] By setting the Bi2O3 content within the above range, the specific gravity is reduced, and an optical glass with reduced ultraviolet transmittance is obtained. On the other hand, if the Bi2O3 content is too high, the partial dispersion ratio Pg,F increases, the specific gravity increases, and Bi ions absorb light of a specific wavelength, which may reduce the transmittance in the short wavelength range as well as the internal transmittance. In addition, the amount of corrosion of the platinum in the glass may increase, which may increase the coloring of the glass.

[0074] In the optical glass according to the first embodiment, the total content of WO3 and Bi2O3 [WO3 + Bi2O3] is preferably 3% or less, more preferably 2.4% or less, 1.9% or less, 1.4% or less, 0.9% or less, and 0.4% or less in that order. It is particularly preferable that WO3 and Bi2O3 are not contained.

[0075] By setting the total content [WO3+Bi2O3] within the above range, it is possible to suppress a decrease in the internal transmittance, particularly in the visible light region.

[0076] In the optical glass according to the first embodiment, the upper limit of the Li2O content is preferably 15.0%, and more preferably 10.0%, 7.0%, 5.0%, 3.0%, and 2.0%, in that order. The lower limit of the Li2O content is preferably 0.0%, and more preferably 0.1%, 0.5%, 1.0%, and 1.5%, in that order.

[0077] By setting the content of Li2O within the above range, the filling rate of the glass structure is increased, and an optical glass with a high refractive index and a low specific gravity is obtained. In addition, the meltability of the glass can be improved and the specific resistance of the molten glass can be reduced. Furthermore, there is an effect of suppressing reduction coloring that may occur when the glass is melted. On the other hand, if the content of Li2O is too low, the transmittance of the glass may decrease. If the content of Li2O is too high, the chemical durability and weather resistance may decrease, and the stability during reheating may decrease.

[0078] In the optical glass according to the first embodiment, the upper limit of the Na2O content is preferably 15.0%, and more preferably 10.0%, 7.0%, 5.0%, 3.0%, and 2.0%, in that order. The lower limit of the Na2O content is preferably 0.0%, and more preferably 0.1%, 0.5%, 1.0%, and 1.5%, in that order.

[0079] By setting the Na2O content within the above range, an optical glass with a reduced specific gravity can be obtained. In addition, the meltability of the glass can be improved, and the specific resistance of the molten glass can be reduced. On the other hand, if the Na2O content is too low, the meltability of the glass may decrease. If the Na2O content is too high, the refractive index may decrease.

[0080] In the optical glass according to the first embodiment, the upper limit of the K2O content is preferably 15.0%, and more preferably 10.0%, 5.0%, 4.0%, 3.0%, 2.0%, and 1.0%, in that order. The lower the K2O content, the more preferable it is, and the lower limit is preferably 0.0%, and more preferably 0.1%, 0.3%, 0.6%, and 0.9%, in that order.

[0081] By setting the content of K2O within the above range, the stability of the TiO2-containing glass can be improved. Also, the meltability of the glass can be improved. On the other hand, if the content of K2O is too high, the refractive index may be significantly reduced.

[0082] In the optical glass according to the first embodiment, the upper limit of the Cs2O content is preferably 15.0%, and more preferably 10.0%, 5.0%, 4.0%, 3.0%, 2.0%, and 1.0%, in that order. The lower limit of the Cs2O content is preferably 0.0%. The Cs2O content may be 0.0%.

[0083] Cs2O has the function of improving the meltability and thermal stability of glass, but if the Cs2O content is too high, the refractive index may decrease significantly and the chemical durability of the glass may deteriorate.

[0084] In the optical glass according to the first embodiment, the upper limit of the MgO content is preferably 10.0%, and more preferably 5.0%, 4.0%, 3.0%, 2.0%, and 1.0%, in that order. The lower the MgO content, the more preferable it is, and the lower limit is preferably 0.0%. The MgO content may be 0.0%.

[0085] By setting the content of MgO within the above range, the stability of the glass can be improved and coloring of the glass can be reduced. On the other hand, if the content of MgO is too high, it may not be possible to simultaneously achieve a high refractive index and a low specific gravity.

[0086] In the optical glass according to the first embodiment, the upper limit of the CaO content is preferably 30.0%, and more preferably 25.0%, 20.0%, 16.0%, and 13.0%, in that order. The lower limit of the CaO content is preferably 0.0%, and more preferably 3.0%, 6.0%, 8.0%, and 10.0%, in that order.

[0087] By setting the CaO content within the above range, an optical glass having a high refractive index, a low specific gravity, and improved meltability can be obtained. On the other hand, if the CaO content is too low, it may be difficult to achieve both a high refractive index and a low specific gravity. Also, if the CaO content is too high, the amount of brick erosion increases, high dispersion cannot be maintained, the thermal stability of the glass decreases, and the devitrification resistance may decrease.

[0088] In the optical glass according to the first embodiment, the upper limit of the SrO content is preferably 10.0%, and more preferably 7.0%, 5.0%, 3.0%, 2.5%, and 2.0%, in that order. The lower the SrO content, the more preferable it is, and the lower limit is preferably 0.0%, and more preferably 0.1%, 0.5%, 1.0%, and 1.5%, in that order.

[0089] By setting the SrO content within the above range, the meltability can be improved. On the other hand, if the SrO content is too high, the specific gravity increases, high dispersibility cannot be maintained, the thermal stability of the glass decreases, and there is a risk of the devitrification resistance decreasing.

[0090] In the optical glass according to the first embodiment, the upper limit of the BaO content is preferably 30.0%, and more preferably 25.0%, 20.0%, 16.0%, and 13.0%, in that order. The lower limit of the BaO content is preferably 0.0%, and more preferably 3.0%, 6.0%, 8.0%, and 10.0%, in that order. The BaO content may be 0.0%.

[0091] By setting the content of BaO within the above range, the melting property can be improved. On the other hand, if the content of BaO is too low, the stability of the glass may be reduced. Also, if the content of BaO is too high, the specific gravity increases significantly, high dispersibility cannot be maintained, the thermal stability of the glass may be reduced, and the devitrification resistance may be reduced.

[0092] In the optical glass according to the first embodiment, the upper limit of the ZnO content is preferably 10.0%, and more preferably 5.0%, 4.0%, 3.0%, 2.0%, and 1.0%, in that order. The lower the ZnO content, the more preferable it is, and the lower limit is preferably 0.0%. The ZnO content may be 0.0%.

[0093] By setting the ZnO content within the above range, it is possible to lower the glass transition temperature Tg. On the other hand, if the ZnO content is too high, the specific gravity increases and the stability of the glass may be impaired.

[0094] In the optical glass according to the first embodiment, the upper limit of the La2O3 content is preferably 10.0%, and more preferably 5.0%, 4.0%, 3.0%, 2.0%, and 1.0%, in that order. The lower limit of the La2O3 content is preferably 0.0%.

[0095] By setting the content of La2O3 within the above range, it is possible to obtain an optical glass with a high refractive index without deteriorating the internal transmittance of the glass. On the other hand, if the content of La2O3 is low, the refractive index tends to decrease. Also, if the content of La2O3 is too high, the specific gravity increases, and the thermal stability of the glass may decrease.

[0096] In the optical glass according to the first embodiment, the upper limit of the Gd2O3 content is preferably 10.0%, and more preferably 5.0%, 4.0%, 3.0%, 2.0%, and 1.0%, in that order. The lower the Gd2O3 content, the more preferable it is, and the lower limit is preferably 0.0%.

[0097] By setting the content of Gd2O3 within the above range, it is possible to obtain optical glass with a high refractive index without deteriorating the internal transmittance of the glass. On the other hand, if the content of Gd2O3 is too high, the thermal stability of the glass may decrease and the specific gravity may increase. There is also a risk of increasing the manufacturing cost of the glass.

[0098] In the optical glass according to the first embodiment, the upper limit of the Y2O3 content is preferably 10.0%, and more preferably 8.0%, 5.0%, 3.0%, 2.0%, and 1.5%, in that order. The lower limit of the Y2O3 content is preferably 0.0%.

[0099] By incorporating Y2O3 in place of, for example, ZrO2 or Nb2O5 within the above range, an optical glass with a high refractive index and low specific gravity can be obtained without deteriorating the internal transmittance of the glass. On the other hand, if the content of Y2O3 is low, the refractive index tends to decrease. Also, if the content of Y2O3 is too high, the thermal stability of the glass may decrease, and the resistance to devitrification may decrease.

[0100] In the optical glass according to the first embodiment, the upper limit of the GeO2 content is preferably 10.0%, and more preferably 6.0%, 4.0%, 3.0%, 2.0%, and 1.0%, in that order. The lower the GeO2 content, the more preferable it is, and the lower limit is preferably 0.0%.

[0101] GeO2 is an expensive glass component, and if the GeO2 content is too high, the manufacturing cost may increase.

[0102] In the optical glass according to the first embodiment, the upper limit of the Ta2O5 content is preferably 5%, and more preferably 3%, 2%, and 1%, in that order. The lower limit of the Ta2O5 content is preferably 0%.

[0103] Ta2O5 is a glass component that acts to increase the refractive index without deteriorating the internal transmittance of the glass, and is also a component that reduces the partial dispersion ratio Pg,F. On the other hand, Ta2O5 is an expensive glass component, and if the content of Ta2O5 increases, the manufacturing cost may increase. In addition, the specific gravity may increase. Therefore, the content of Ta2O5 is preferably within the above range.

[0104] In the optical glass according to the first embodiment, the content of Sc2O3 is preferably 2% or less. The lower limit of the content of Sc2O3 is preferably 0%.

[0105] Sc2O3 has the effect of increasing the refractive index of the glass, but is an expensive component, so the content of each of Sc2O3 is preferably within the above range.

[0106] In the optical glass according to the first embodiment, the upper limit of the HfO2 content is preferably 2%, further preferably 1.5%, 1.0%, 0.5%, or 0.3%, and the lower limit of the HfO2 content is preferably 0%, further preferably 0.005%, 0.01%, 0.03%, 0.05%, 0.07%, or 0.09%, in that order.

[0107] Note that a certain amount of HfO2 may be contained in the raw material of ZrO2. Therefore, a glass containing ZrO2 may contain a certain amount of HfO2. Therefore, in the optical glass according to the first embodiment, the mass ratio [HfO2 / ZrO2] of the content of HfO2 to the content of ZrO2 may also be within a certain range. For example, the lower limit of the mass ratio [HfO2 / ZrO2] may be 0.005, or may be 0.010, 0.013, or 0.015. On the other hand, the upper limit of the mass ratio may be 0.05, or may be 0.040, 0.030, 0.020, or 0.018. From the viewpoint of suppressing the melting of the components of the refractory brick into the glass, it is preferable that the glass contains a small amount of ZrO2, and therefore the content of HfO2 is preferably within the above range.

[0108] In the optical glass according to the first embodiment, the content of Lu2O3 is preferably 2% or less. The lower limit of the content of Lu2O3 is preferably 0%.

[0109] Lu2O3 has the function of adjusting the refractive index of the glass, but because it has a large molecular weight, it is also a glass component that increases the specific gravity of the glass, so the content of Lu2O3 is preferably within the above range.

[0110] In the optical glass according to the first embodiment, the content of Yb2O3 is preferably 2% or less, more preferably 1% or less, and further preferably 0.5% or less. The lower limit of the content of Yb2O3 is preferably 0%.

[0111] Yb2O3 adjusts the refractive index of the glass, but because of its large molecular weight, it increases the specific gravity of the glass. When the specific gravity of the glass increases, the mass of the optical element increases. Therefore, it is desirable to reduce the Yb2O3 content and suppress the increase in the specific gravity of the glass.

[0112] Moreover, if the content of Yb2O3 is too high, the thermal stability of the glass is reduced. Furthermore, it brings about absorption in the infrared region. From the viewpoint of preventing the deterioration of the thermal stability of the glass and suppressing an increase in the specific gravity, the content of Yb2O3 is preferably within the above range.

[0113] The optical glass according to the first embodiment is preferably composed mainly of the above-mentioned glass components, namely Al2O3, SiO2, ZrO2, P2O5, B2O3, TiO2, Nb2O5, WO3, Bi2O3, Li2O, Na2O, K2O, Cs2O, MgO, CaO, SrO, BaO, ZnO, La2O3, Gd2O3, Y2O3, GeO2, Ta2O5, Sc2O3, HfO2, Lu2O3, and Yb2O3, and the total content of the above-mentioned glass components is preferably 95% or more, more preferably 98% or more, even more preferably 99% or more, and even more preferably 99.5% or more.

[0114] The optical glass according to the first embodiment is preferably composed essentially of the above glass components, but may contain other components as long as they do not impair the effects of the present invention. Furthermore, the present invention does not exclude the inclusion of unavoidable impurities.

[0115] (Other Ingredients) Pb, As, Cd, Tl, Be, and Se are all toxic, so it is preferable that the optical glass according to this embodiment does not contain these elements as glass components.

[0116] U, Th, and Ra are all radioactive elements, and therefore it is preferable that the optical glass according to this embodiment does not contain these elements as glass components.

[0117] V, Cr, Mn, Fe, Co, Ni, Cu, Pr, Nd, Pm, Sm, Eu, Tb, Dy, Ho, Er, and Tm can increase the coloring of the glass and become a source of fluorescence. Therefore, it is preferable that the optical glass according to this embodiment does not contain these elements as glass components. However, elements that do not deteriorate the transmittance around 460 nm, which is the object of the present invention, can be introduced to the extent that the problem of the present invention can be solved.

[0118] Sb (Sb2O3) and Ce (CeO2) are optional elements that function as fining agents. Of these, Sb (Sb2O3) is a fining agent with a large fining effect. Ce (CeO2) has a smaller fining effect than Sb (Sb2O3). Ce (CeO2) tends to intensify the coloring of glass when added in large amounts.

[0119] The content of Sb2O3 is expressed as an exclusive percentage. That is, when the total content of all glass components other than Sb2O3 and CeO2 is 100 mass%, the content of Sb2O3 is preferably 1.0 mass% or less, and more preferably 0.4 mass% or less, 0.2 mass% or less, 0.1 mass% or less, 0.05 mass% or less, 0.03 mass% or less, 0.02 mass% or less, and 0.01 mass% or less in that order. The content of Sb2O3 may be 0 mass%.

[0120] The CeO2 content is also expressed as an exclusive ratio. That is, when the total content of all glass components other than CeO2 and Sb2O3 is taken as 100 mass%, the CeO2 content is preferably 2 mass% or less, more preferably 1 mass% or less, further preferably 0.5 mass% or less, and even more preferably 0.1 mass% or less. The CeO2 content may be 0 mass%. By setting the CeO2 content in the above range, the clarity of the glass can be improved.

[0121] (Glass characteristics) <Refractive index nd> In the optical glass according to the first embodiment, the upper limit of the refractive index nd can be 2.50, or can be 2.20, 2.10, 2.05, 2.00, or 1.98. The lower limit of the refractive index nd can be 1.85, or can be 1.87, 1.89, or 1.90. The refractive index can be controlled by adjusting the content of glass components that contribute to a high refractive index, such as TiO2, Nb2O5, ZrO2, and Y2O3, adjusting the content of low refractive index components, such as SiO2, Al2O3, and B2O3, or by introducing modifying components, such as Li2O and CaO.

[0122] <Abbe number νd> In the optical glass according to the first embodiment, the upper limit of the Abbe number νd can be 30.0, or can be 28.0, 26.0, 25.0, or 24.5. The lower limit of the Abbe number νd can be 15.0, or can be 18.0, 20.0, 22.0, or 23.0. By setting the Abbe number νd within the above range, a glass having a desired dispersibility can be obtained. The Abbe number νd can be controlled by adjusting the contents of TiO2, Nb2O5, WO3, ZrO2, and Bi2O3, which are glass components that contribute to high dispersion.

[0123] <Specific gravity of glass> The optical glass according to the first embodiment is a high refractive index glass, but does not have a large specific gravity. If the specific gravity of the glass can be reduced, the weight of the lens can be reduced. On the other hand, if the specific gravity is too low, it will lead to a decrease in thermal stability.

[0124] Therefore, in the optical glass according to the first embodiment, the upper limit of the specific gravity is preferably 7.0, and more preferably 6.0, 5.0, 4.5 and 4.0 in that order. The lower limit of the specific gravity is preferably 2.5, and more preferably 3.0 and 3.5 in that order.

[0125] The specific gravity is determined by the atomic weight of the components in the glass and the volume occupied by those atoms. For example, when an oxide containing a sixth period element or an element with a large atomic number of 57 or higher is introduced, the specific gravity tends to increase, but if the volume occupied by that element is also large, the increase in specific gravity may be suppressed. However, if the volume occupied by an element is too large, the refractive index decreases. In addition, the volume occupied by an element is not specific, and changes slightly depending on the presence of other glass components. In this way, the specific gravity value can be controlled by adjusting the total amount and ratio of each component. Furthermore, the volume occupied by each element changes slightly depending on the annealing conditions of the glass.

[0126] <Glass transition temperature Tg> In one example of the optical glass according to the first embodiment, the upper limit of the glass transition temperature Tg is not particularly limited, but in consideration of productivity such as the time required for slow cooling, it is preferably 850° C., and more preferably 800° C., 750° C., 700° C., and 650° C. in that order. There is also no particular limit on the lower limit of the glass transition temperature Tg, but from the viewpoint of providing the optical glass with appropriate heat resistance, it is preferably 100° C., and more preferably 200° C., 300° C., 400° C., and 500° C. in that order.

[0127] The glass transition temperature Tg can be controlled by incorporating components such as Li and Zn, which are known to lower the Tg, into the glass components to be introduced, as well as by increasing or decreasing the amount of glass-forming components and adjusting the ratio of each component.

[0128] By setting the upper limit of the glass transition temperature Tg within the above range, increases in the molding temperature and annealing temperature during reheat press of the glass can be suppressed, and thermal damage to the reheat press molding equipment and annealing equipment can be reduced.

[0129] When the lower limit of the glass transition temperature Tg satisfies the above range, it becomes easier to maintain good reheat press moldability and good thermal stability of the glass while maintaining the desired Abbe number and refractive index.

[0130] <Liquidus temperature LT> The upper limit of the liquidus temperature LT of the optical glass according to the first embodiment is preferably 1450 °C, more preferably 1400 °C, 1350 °C, 1300 °C, 1250 °C, and 1200 °C in this order, from the viewpoint of minimizing the energy used for melting the glass. There is no particular limitation on the lower limit of the liquidus temperature, but from the viewpoint of obtaining a certain stability, it is preferably 800 °C, more preferably 900 °C, 1000 °C, 1050 °C, and 1100 °C in this order. By setting the liquidus temperature within the above range, erosion of the refractory bricks during glass melting can be suppressed.

[0131] The liquidus temperature is determined as follows. 10 cc (10 ml) of glass is put into a platinum crucible, melted at 1250 °C to 1450 °C for 20 to 30 minutes, then cooled to below the glass transition temperature Tg, and the glass together with the platinum crucible is placed in a melting furnace at a predetermined temperature and held for 2 hours. The holding temperature is 800 °C or higher, in increments of 5 °C or 10 °C. After holding for 2 hours, it is cooled, and the presence or absence of crystals inside the glass is observed with a 100-fold optical microscope. The lowest temperature at which no crystals are precipitated is taken as the liquidus temperature.

[0132] <Pt content> In the optical glass according to the first embodiment, the upper limit of the Pt content is preferably 10.0 mass ppm, more preferably 8.0 mass ppm, 7.0 mass ppm, 6.0 mass ppm, and 5.0 mass ppm in this order. It is preferable that the Pt content is less, and the lower limit is preferably 4.0 mass ppm, and it is more preferable that it is less in the order of 3.0 mass ppm, 2.0 mass ppm, and 0.0 mass ppm.

[0133] In the case of glass produced in a melting furnace using refractory bricks, particularly in the part of the melting furnace where the batch raw materials are heated and melted, the Pt content is reduced compared to the glass produced in a platinum furnace. By setting the Pt content within the above range, an optical glass with excellent transmittance can be obtained.

[0134] <τ460, τ440> In the optical glass according to the first embodiment, the lower limit of the internal transmittance τ460 at a wavelength of 460 nm at a thickness of 10.0 mm±0.1 mm is preferably 88.0%, and more preferably 90.0%, 91.0%, 92.0%, 93.0%, 94.0%, and 95.0% in that order. The higher the internal transmittance, the more preferable it is, and it is preferably 100.0%, and the higher the upper limit, the more preferable it is, in the order of 99.0%, 98.0%, 97.0%, and 96.0%. The thickness (optical path length) of the glass product using the optical glass according to this embodiment is appropriately selected depending on its application, and is not limited to 10.0 mm, and can be, for example, 15 mm or more, further 20 mm or more, or 30 mm or more, or can be 8 mm or less, 6 mm or less, or 4 mm or less depending on the application.

[0135] In the optical glass according to the first embodiment, the lower limit of the internal transmittance τ440 at a wavelength of 440 nm and a thickness of 10.0 mm±0.1 mm is preferably 85.0%, and more preferably 88.0%, 90.0%, 91.0%, 92.0%, 93.0%, and 94.0% in that order. The higher the internal transmittance, the more preferable it is, and it is preferably 100.0%, and the upper limit is preferably 99.0%, 98.0%, 97.0%, 96.0%, and 95.0% in that order.

[0136] The internal transmittance (τ) is the transmittance excluding the surface reflection loss on the entrance side and exit side. For two glass samples with different thicknesses, the measured transmittance including the surface reflection loss at wavelengths of 460 nm and 440 nm is used to calculate the internal transmittance using the following formula. The thicknesses d1 and d2 of the glass samples are 2.0 mm ± 0.1 mm and 10.0 mm ± 0.1 mm, respectively.

number

[0137] Internal transmittance is the transmittance of a material that is not dependent on the refractive index, and can be controlled by adjusting the inherent light absorption of the elements contained in the glass, the light absorption due to impurities such as Pt, and even the absorption due to color centers that occur within the glass skeleton. From the above viewpoint, the internal transmittance can be controlled within the above range by adjusting the content of components that reduce the internal transmittance, such as WO3 and Bi2O3. It is also effective to adjust the content of trace components, such as Sb2O3 and Pt. It is also effective to adjust the content of alkali components, such as βOH, Li2O, Na2O, and K2O, to reduce reduction coloring.

[0138] <λτ90, λτ80, λτ5> In the optical glass according to the first embodiment, the light transmittance can also be evaluated by λτ90, λτ80, and λτ5. For example, λτ90 is the wavelength at which the internal transmittance is 90% as shown in FIG. 1. Similarly, λτ80 and λτ5 are the wavelengths at which the internal transmittance is 80% and 5%, respectively. The internal transmittance is calculated by the above formula.

[0139] In the optical glass according to the first embodiment, the upper limit of λτ90 is preferably 500 nm, more preferably 470 nm, 450 nm, 430 nm, and 420 nm, in order, from the viewpoint of increasing the transmittance at a desired wavelength. There is no particular restriction on the lower limit of λτ90, but from the viewpoint of reducing the transmittance of short-wavelength light that adversely affects the human body, it is preferably 150 nm, more preferably 200 nm, 250 nm, 300 nm, and 350 nm, in order.

[0140] In the optical glass according to the first embodiment, the upper limit of λτ80 is preferably 450 nm from the viewpoint of increasing the transmittance at a desired wavelength, and more preferably 440 nm, 430 nm, 420 nm, and 410 nm in that order. There is no particular restriction on the lower limit of λτ80, but from the viewpoint of reducing the transmittance of short-wavelength light that adversely affects the human body, it is preferably 150 nm, and more preferably 200 nm, 250 nm, 300 nm, and 350 nm in that order.

[0141] In the optical glass according to the first embodiment, the upper limit of λτ5 is preferably 390 nm, more preferably 380 nm, 370 nm, 365 nm, and 360 nm, in that order, from the viewpoint of increasing the transmittance at a desired wavelength. There is no particular restriction on the lower limit of λτ5, but from the viewpoint of reducing the transmittance of short-wavelength light that adversely affects the human body, it is preferably 150 nm, more preferably 250 nm, 300 nm, 330 nm, 350 nm, and 355 nm, in that order.

[0142] <λ70> In the optical glass according to the first embodiment, the upper limit of λ70 is preferably 435 nm from the viewpoint of increasing the transmittance at a desired wavelength, and more preferably 430 nm, 425 nm, 420 nm, 415 nm, 410 nm, 405 nm, and 400 nm in that order. There is no particular restriction on the lower limit of λ70, but from the viewpoint of achieving compatibility with a high refractive index, it is preferably 300 nm, and more preferably 310 nm, 320 nm, 330 nm, 340 nm, and 350 nm in that order.

[0143] Since λ70, which is an external transmittance of 70%, is determined by the internal transmittance and refractive index of the glass, it is not the optimal index for expressing the properties of the glass of the present invention. However, as a guideline, it is preferable that the glass has λ70 in the above range.

[0144] (Optical glass manufacturing) The optical glass according to the embodiment of the present invention may be produced by mixing glass raw materials to obtain the above-mentioned predetermined composition, and by using the mixed glass raw materials according to a known glass manufacturing method. For example, a plurality of compounds may be mixed and mixed sufficiently to obtain a batch raw material, and the batch raw material may be placed in a crucible made of refractory bricks, heated to obtain a molten glass, and then clarified and homogenized, and the molten glass may be formed and slowly cooled to obtain an optical glass. The clarification and homogenization steps may be appropriately performed in a platinum crucible. When melting in a platinum crucible, melting may be performed in a non-oxidizing atmosphere, i.e., a nitrogen atmosphere or a water vapor atmosphere, in order to suppress oxidation of platinum. A known method may be applied to the forming and slow cooling of the molten glass. The glass raw material may be cullet obtained by quenching a molten glass roughly melted in a refractory brick or a quartz crucible.

[0145] In addition, as long as a desired glass component can be introduced into the glass in a desired content, the compound used when preparing the batch raw materials is not particularly limited. Examples of such compounds include oxides, carbonates, nitrates, hydroxides, hydrates, fluorides, chlorides, and the like.

[0146] In addition, the amount of hydroxyl groups in the glass may be controlled as a means for suppressing oxidation of glass components by Pt, which may be introduced from a platinum crucible. Since the optical glass according to this embodiment is a glass mainly composed of silicate, the introduction of excess hydroxyl groups may break the glass structure and reduce the thermal stability of the glass. This thermal stability affects the degree of crystal precipitation that occurs when the molten glass is slowly cooled, and also affects crystal precipitation when the glass is reheated. In the case of the optical glass according to this embodiment, since the latter effect is large, it is preferable to appropriately control the amount of hydroxyl groups.

[0147] The amount of hydroxyl groups in glass can be expressed by the value of βOH. In the optical glass according to the first embodiment, the lower limit of the value of βOH shown in the following formula (1) is preferably 0.1 mm -1 and even 0.2 mm -1 , 0.3mm -1, 0.4mm -1 The upper limit of the βOH value is preferably 1.5 mm. -1 and even 1.2 mm -1 , 1.0mm -1 , 0.9mm -1 , 0.8mm -1 , 0.7mm -1 , 0.6mm -1 The order of preference is: βOH=-[ln(B / A)] / t …(1)

[0148] In the formula (1), t represents the thickness (mm) of the glass used in measuring the external transmittance, A represents the external transmittance (%) at a wavelength of 2500 nm when light is incident on the glass parallel to its thickness direction, B represents the external transmittance (%) at a wavelength of 2900 nm when light is incident on the glass parallel to its thickness direction, and ln is the natural logarithm.

[0149] The "external transmittance" is the intensity of incident light I in Intensity of light transmitted through glass vs. I out The ratio (I out / I in ), that is, the transmittance taking into account surface reflection on the glass surface, and the transmittance is obtained by measuring the transmission spectrum using a spectrophotometer.

[0150] By evaluating βOH, the content of water (and / or hydroxide ions, hereinafter simply referred to as "water") in the glass can be evaluated. That is, a glass with a high βOH value means that the water content in the glass is high.

[0151] By setting the value of βOH within the above range, devitrification is suppressed and an optical glass with high transmittance can be obtained. On the other hand, if the value of βOH in the present invention is too high, the thermal stability of the glass tends to decrease when it is reheated to above the glass transition point. In addition, during the annealing process of the glass, that is, during holding the glass at a temperature higher than the strain point and lower than the yield point for minutes or hours, there is a risk that the glass will become cloudy or devitrified.

[0152] The method for controlling the βOH value is not particularly limited, but examples thereof include using a raw material containing water as the glass raw material, adding water vapor to the melting atmosphere in the melting step, etc. When melting glass in a melting furnace using refractory bricks, the molten glass is indirectly heated by a gas burner, and water generated by the combustion of the gas burner is introduced into the molten glass at this time. This appropriately increases the amount of water in the molten glass, making it possible to set the βOH value within the above range.

[0153] (Manufacturing of optical elements, etc.) To manufacture an optical element using the optical glass according to the embodiment of the present invention, a known method may be applied. For example, in the manufacture of the optical glass, molten glass is poured into a mold and molded into a plate shape to manufacture a glass material made of the optical glass according to the present invention. The obtained glass material is appropriately cut, ground, and polished to manufacture cut pieces of a size and shape suitable for press molding. The cut pieces are heated and softened, and press molded (reheat pressed) by a known method to manufacture an optical element blank that is similar to the shape of the optical element. The optical element blank is annealed, and ground and polished by a known method to manufacture an optical element.

[0154] The optically functional surface of the prepared optical element may be coated with an anti-reflection film, a total reflection film, or the like depending on the intended use.

[0155] According to one aspect of the present invention, an optical element made of the optical glass can be provided. Examples of the types of optical elements include lenses such as flat lenses, spherical lenses, and aspherical lenses, prisms, and diffraction gratings. Examples of the lens shapes include biconvex lenses, plano-convex lenses, biconcave lenses, plano-concave lenses, convex meniscus lenses, and concave meniscus lenses. The optical element can be manufactured by a method including a process of processing a glass molded body made of the optical glass. Examples of the processing include cutting, milling, rough grinding, fine grinding, and polishing. When such processing is performed, breakage can be reduced by using the glass, and high-quality optical elements can be stably supplied.

[0156] Second embodiment The optical glass according to the second embodiment of the present invention is The total content of TiO2 and Nb2O5 [TiO2+Nb2O5] is 20% or more, The mass ratio of the Al2O3 content to the total content of SiO2 and ZrO2 [(Al2O3 / (SiO2+ZrO2)]] is greater than 0.0000.

[0157] In the optical glass according to the second embodiment, the total content of TiO2 and Nb2O5 [TiO2+Nb2O5] is 20% or more. The lower limit of the total content is preferably 22%, and more preferably 24%, 26%, 28%, 33%, 37%, 40%, and 42% in that order. The upper limit of the total content is preferably 70%, and more preferably 60%, 57%, 55%, 53%, 50%, and 46% in that order.

[0158] TiO2 and Nb2O5 are components that contribute to a high refractive index without increasing the specific gravity. Therefore, in order to obtain a glass that has both the desired specific gravity and refractive index characteristics, the total content of TiO2 and Nb2O5 is preferably within the above range.

[0159] In the optical glass according to the second embodiment, the mass ratio of the Al2O3 content to the total content of SiO2 and ZrO2 [(Al2O3 / (SiO2+ZrO2)] is greater than 0.0000. The lower limit of the mass ratio [(Al2O3 / (SiO2+ZrO2)] is preferably 0.0001, and more preferably 0.0003, 0.0005, 0.0007, 0.0010, 0.0050, 0.0100, 0.0200, 0.0250, 0.0350, and 0.0450, in that order. The upper limit of the mass ratio is preferably 0.3000, and more preferably 0.2500, 0.2000, 0.1500, and 0.1000, in that order.

[0160] By setting the mass ratio [(Al2O3 / (SiO2+ZrO2)] within the above range, it is possible to suppress erosion of the refractory bricks during glass melting. Furthermore, compared with glasses having a ratio outside the above range, this has the effect of increasing thermal stability and delaying devitrification during heating or crystal precipitation when the molten glass is cooled. On the other hand, if the mass ratio is too large, not only does the refractive index nd decrease, but the thermal stability also decreases, and there is a risk of devitrification.

[0161] Hereinafter, preferred aspects of the optical glass according to the second embodiment will be described.

[0162] In the optical glass according to the second embodiment, the upper limit of the mass ratio of the total content of B2O3 and P2O5 to the total content of SiO2 and Al2O3 [(B2O3+P2O5) / (SiO2+Al2O3)] is preferably 0.30, and more preferably 0.26, 0.21, 0.18, 0.16, 0.15, 0.14, 0.12, 0.10, 0.90, and 0.08 in that order. The lower limit of the mass ratio is preferably 0.00, and more preferably 0.01, 0.02, 0.03, 0.04, and 0.05 in that order.

[0163] By setting the mass ratio [(B2O3+P2O5) / (SiO2+Al2O3)] in the above range, it is possible to suppress erosion of the vitreous matter of the refractory bricks during glass melting. If the mass ratio is too large, the erosion of the refractory bricks becomes significant, which may reduce the homogeneity of the molten glass and decrease the devitrification resistance.

[0164] In the optical glass according to the second embodiment, the upper limit of the mass ratio of the total content of BaO, La2O3, Gd2O3, and WO3 to the total content of CaO, SrO, and Y2O3 [(BaO+La2O3+Gd2O3+WO3) / (CaO+SrO+Y2O3)] is preferably 3.0, and more preferably 2.7, 2.0, 1.9, 1.8, 1.7, and 1.6 in that order. The lower limit of the mass ratio is preferably 0.0, and more preferably 0.5, 0.8, 1.0, and 1.2 in that order.

[0165] By setting the mass ratio [(BaO+La2O3+Gd2O3+WO3) / (CaO+SrO+Y2O3)] in the above range, it is possible to limit the amount of components with too large atomic weights or high refractive index components that promote oxygen filling, and to reduce the specific gravity of the glass. On the other hand, if the mass ratio is too large, the specific gravity of the glass increases, decreasing the kinetic viscosity of the molten glass, making it difficult to control the glass flow, and there is a risk of productivity deteriorating. There is also a risk of increased erosion of the refractory bricks.

[0166] In the optical glass according to the second embodiment, the upper limit of the total content of Li2O, Na2O, and K2O [Li2O+Na2O+K2O] is preferably 13%, more preferably 11%, 10%, 8.0%, 6.0%, 5.0%, and 4.0%, in that order. The lower limit of the total content is preferably 0.00%, more preferably 0.01%, 0.1%, 0.5%, 1.0%, 1.5%, 2.0%, and 3.0%, in that order.

[0167] By setting the total content [Li2O+Na2O+K2O] within the above range, the viscosity of the glass can be appropriately maintained and the productivity of the glass can be improved. In addition, the light absorption caused by the reducing components generated by Ti and Nb can be suppressed, and further, the melting temperature can be lowered and the elimination of electronic defects in the glass due to slow cooling can be promoted, thereby increasing the internal transmittance at 460 nm. In addition, the erosion of the refractory brick during glass melting can be suppressed. On the other hand, if the total content is too small, the melting property of the glass raw material is deteriorated, and it becomes necessary to set the melting temperature of the raw material higher. As a result, the deterioration of the refractory brick is promoted, and the productivity is deteriorated. On the other hand, if the total content is too large, the viscosity of the glass decreases and the thermal stability is decreased accordingly, which may deteriorate the productivity. In addition, the resistivity of the molten glass decreases, which reduces the heating efficiency when the molten glass is heated by passing electricity, which may result in a deterioration of the melting property of the glass and a deterioration of the productivity. The higher the Al2O3 content in the glass, the more desirably the content is adjusted so as not to be too high.

[0168] In the optical glass according to the second embodiment, the lower limit of the Al2O3 content is preferably 0.01%, and more preferably 0.05%, 0.08%, 0.10%, 0.13%, 0.16%, 0.20%, 0.30%, 0.50%, 0.70%, and 1.0%, in that order. The upper limit of the Al2O3 content is preferably 10.0%, and more preferably 8.0%, 6.0%, 4.0%, and 2.0%, in that order.

[0169] When glass is melted in a furnace using refractory bricks, Al2O3 derived from the refractory bricks is introduced into the molten glass. Therefore, even if the glass raw material does not contain Al2O3, a small amount of Al2O3 is contained in the glass produced by melting in a furnace using refractory bricks. When the content of Al2O3 is within the above range, the thermal stability is high, devitrification during heating is suppressed, and crystal precipitation during cooling of the molten glass is suppressed, compared with the case where the content of Al2O3 is outside the above range. However, since Al2O3 is a component that has a small effect of reducing the specific gravity and a function of reducing the refractive index, the lower the content of Al2O3, the more preferable it is from the viewpoint of obtaining a glass with a high refractive index and low specific gravity. In addition, if the content of Al2O3 is too high, the devitrification resistance of the glass decreases, the glass transition temperature Tg increases, and the thermal stability may decrease. On the other hand, if the Al2O3 content is too low, there is a risk of increased erosion of the refractory bricks.

[0170] In the optical glass according to the second embodiment, the contents and ratios of glass components other than those mentioned above can be the same as those in the first embodiment. Furthermore, the glass characteristics, the production of the optical glass, and the production of optical elements, etc. in the second embodiment can also be the same as those in the first embodiment. EXAMPLES

[0171] The present invention will be described in more detail below with reference to examples, although the present invention is not limited to the embodiments shown in the examples.

[0172] Example 1 Glass samples having the glass compositions shown in Tables 1 and 2 were prepared by the following procedure, and various evaluations were carried out.

[0173] [Production of optical glass] First, oxides, hydroxides, carbonates, and nitrates corresponding to the constituent components of the glass were prepared as raw materials, and the raw materials were weighed and mixed so that the glass composition of the optical glass obtained would be the respective compositions shown in Tables 1 and 2, and the raw materials were thoroughly mixed. The thus obtained mixed raw materials (batch raw materials) were placed in a crucible made of a refractory oxide, heated at 1150°C to 1450°C for 1 hour to form molten glass, and transferred to a platinum crucible, stirred to homogenize, clarified, and then cast into a mold preheated to an appropriate temperature. The cast glass was heat-treated for 30 minutes at a temperature 100°C lower than the glass transition temperature Tg, and allowed to cool to room temperature in a furnace to obtain a glass sample. In the examples, the amount of raw materials was about 150 g on an oxide basis.

[0174] [Confirmation of glass composition] The content of each glass component in the obtained glass sample was measured by inductively coupled plasma atomic emission spectrometry (ICP-AES), and it was confirmed that each composition was as shown in Tables 1 and 2.

[0175] [Optical property measurements] The obtained glass sample was further annealed at about the glass transition temperature Tg for about 30 minutes to about 2 hours, and then cooled to room temperature in a furnace at a temperature drop rate of -30°C / hour to obtain an annealed sample. The refractive indices nd, ng, nF, and nC, and Abbe numbers νd, τ460, τ440, λτ90, λτ80, λτ5, and λ70 of the obtained annealed sample were measured. The results are shown in Table 3. (i) Refractive index nd, ng, nF, nC and Abbe number νd The refractive indices nd, ng, nF, and nC of the annealed sample were measured by the refractive index measurement method of JIS B 7071-1 of JIS standard, and the Abbe number vd was calculated according to the following formula. νd=(nd-1) / (nF-nC)

[0176] (ii) τ460, τ440 The internal transmittance (τ460, τ440) at wavelengths of 460 nm and 440 nm was measured. For two glass samples with different thicknesses, the internal transmittance was calculated using the measured transmittance including surface reflection loss at wavelengths of 460 nm and 440 nm, respectively, according to the following formula. The thicknesses d1 and d2 of the glass samples were 2.0 mm ± 0.1 mm and 10.0 mm ± 0.1 mm, respectively.

number

[0177] (iii) λτ90, λτ80, λτ5, λ70 The wavelengths at which the internal transmittance is 90% (λτ90), 80% (λτ80), 5% (λτ5), and 70% (λ70) were measured. The internal transmittance was calculated using the above formula.

[0178] [specific gravity] The specific gravity was measured by Archimedes' method, and the results are shown in Table 3.

[0179] [Glass transition temperature Tg] The glass transition temperature Tg was measured at a heating rate of 10° C. / min using a differential scanning calorimeter (DSC3300SA) manufactured by NETZSCH JAPAN Co., Ltd. The results are shown in Table 3.

[0180] [Liquidus temperature LT] The liquidus temperature LT was determined as follows. 10 cc (10 ml) of glass was placed in a platinum crucible and melted at 1250°C to 1400°C for 20 to 30 minutes, then cooled to below the glass transition temperature Tg. The glass together with the platinum crucible was placed in a melting furnace at a specified temperature and held for 2 hours. The holding temperature was 800°C or higher in 5°C or 10°C increments, and after holding for 2 hours, the glass was cooled and the presence or absence of crystals inside the glass was observed under a 100x optical microscope. The lowest temperature at which no crystals precipitated was taken as the liquidus temperature. The results are shown in Table 3.

[0181] [Pt content] The Pt content was measured by inductively coupled plasma atomic emission spectrometry (ICP-AES). The results are shown in Table 3.

[0182] [Table 1]

[0183] [Table 2]

[0184] [Table 3]

[0185] Example 2 [Refractory brick corrosion test] Glass samples having the glass compositions of Nos. 13, 26, 27, and 28 in Table 1 and Comparative Example A were prepared in the same manner as in Example 1, and the corrosion of the refractory bricks was evaluated in the following manner.

[0186] 40cc of glass sample was heated and melted in a platinum crucible at 1280℃ for 30 minutes. A cylindrical brick sample (AGC Ceramics ZB-1711VF, SiO2:ZrO2:Al2O3 ratio approximately 1:4:5, diameter 20mm, length 100mm) was immersed in the molten glass sample in the platinum crucible and heated at 1280℃ for 72 hours. After heating, the brick sample was taken out.

[0187] The removed brick sample was cut in half lengthwise through the center of the sample. At the cut surface, the width of the sample corresponds to the diameter. A photograph of the cut surface is shown in Figure 1. As shown in Figure 1, in the comparative example, damage such as constrictions was observed in the portion located at the liquid surface of the molten glass sample during immersion. Also, the portion immersed in the molten glass sample was eroded overall, reducing its diameter. On the other hand, in the example, the brick sample did not have any noticeable damage such as constrictions, and the erosion of the portion immersed in the molten glass sample was also small.

[0188] The removed brick samples were evaluated as follows. First, on the fractured surface, as shown in Figure 2, the diameter before the erosion test, the minimum diameter (diameter at the necking position) that occurred near the contact point with the glass liquid surface after the erosion test, and the diameter 25 mm below this necking position were measured. The percentage increase or decrease in diameter after the erosion test and the average increase or decrease ΔD were evaluated based on the following formula. Note that the diameter does not include glass attached to the surface of the brick sample or any altered areas of glass.

[0189] Increase / decrease rate D N (%) = ([Minimum diameter (diameter at the neck position)] - [Diameter before erosion test]) / [Diameter before erosion test] x 100

[0190] Increase / decrease rate D 25 (%) = ([Diameter 25 mm below the neck position after erosion test] - [Diameter before erosion test]) / [Diameter before erosion test] x 100

[0191] Average rate of increase or decrease ΔD = (rate of increase or decrease D N + Increase / decrease rate D 25 ) / 2

[0192] In the above formula, the diameter of the brick sample was measured three times using a digital caliper that can display to the nearest 0.01 mm, and the average value (unit: mm) was rounded off to the first decimal place to obtain the first decimal place. Based on the absolute value of the average rate of increase or decrease ΔD (|ΔD|), the degree of erosion was determined by classifying it as shown in Table 4. The results are shown in Table 5.

[0193] [Table 4]

[0194] [Table 5]

[0195] Example 3 Using each of the optical glasses produced in Example 1, lens blanks were produced by a known method, and the lens blanks were processed by a known method such as polishing to produce various lenses. The optical lenses produced include various lenses such as a flat lens, a biconvex lens, a biconcave lens, a plano-convex lens, a plano-concave lens, a concave meniscus lens, a convex meniscus lens, etc. Here, the optical glass can be cut without being softened by heating to obtain a lens blank. By combining each lens with a lens made of a different type of optical glass, secondary chromatic aberration can be effectively corrected.

[0196] In addition, because the glass has a low specific gravity, each lens is lighter than a lens having the same optical properties and size, making them suitable for use in goggle-type or eyeglass-type AR display devices. In the same manner, prisms were produced using the various optical glasses produced in Example 1.

[0197] The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present invention is defined by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims.

[0198] For example, by adjusting the composition as described in the specification to the glass compositions exemplified above, an optical glass according to one aspect of the present invention can be produced. Furthermore, it is of course possible to arbitrarily combine two or more of the items described in the specification as examples or preferred ranges.

Claims

1. The refractive index nd is 1.85 or more, BaO, La 2 O 3 , Gd 2 O 3 , and W.O. 3 The total content of CaO, SrO, and Y 2 O 3 The mass ratio of the total content of BaO + La 2 O 3 +Gd 2 O 3 +W.O. 3 ) / (CaO+SrO+Y 2 O 3 ) is 2.0 or less, B 2 O 3 and P 2 O 5 The total content of and SiO 2 and Al 2 O 3 The mass ratio of the total content of [(B 2 O 3 +P 2 O 5 ) / (SiO 2 +Al 2 O 3 ) is 0.10 or less, Li 2 O, Na 2 O, and K 2 The total content of O [Li 2 O+Na 2 O+K 2 O] is 1.0 mass% or more and 10 mass% or less, A 2 O 3 Content and SiO 2 and ZrO 2 The mass ratio of [Al 2 O 3 / (SiO 2 + ZrO 2 ) is greater than 0.0000, TiO 2 , Nb 2 O 5 , and ZrO 2 The total content [TiO 2 +Nb 2 O 5 + ZrO 2 ] is 35 mass% or more, A 2 O 3 The content is 0.005 mass% or more, SiO 2 The content is 5.0% by mass or more, The CaO content is 6.0% by mass or more, TiO 2 The content is 14.0% by mass or more, Nb 2 O 5 The content is 10.0 mass% or more, TiO 2 and Nb 2 O 5 The total content [TiO 2 +Nb 2 O 5 ] is 20 mass% or more, A 2 O 3 , SiO 2 , ZrO 2 , P 2 O 5 , B 2 O 3 , TiO 2 , Nb 2 O 5 , W.O. 3 , Bi 2 O 3 , Li 2 O, Na 2 O.K. 2 O, Cs 2 O, MgO, CaO, SrO, BaO, ZnO, La 2 O 3 , Gd 2 O 3 , Y 2 O 3 , GeO 2 , Ta 2 O 5 , Sc 2 O 3 , HfO 2 , Lu 2 O 3 , and Yb 2 O 3 The total content is 95% by mass or more, P 2 O 5 The content is 1.0 mass% or less, B 2 O 3 The content is 6.0 mass% or less, WO 3 The content is 1.0 mass% or less, Bi 2 O 3 The content is 1.0 mass% or less, Cs 2 The content of O is 1.0 mass% or less, The content of MgO is 5.0 mass% or less, The content of SrO is 5.0 mass% or less, The content of BaO is 25.0 mass% or less, The ZnO content is 5.0 mass% or less, La 2 O 3 The content is 11.76 mass% or less, G.D. 2 O 3 The content is 1.0 mass% or less, Y 2 O 3 The content is 8.0 mass% or less, GeO 2 The content is 1.0 mass% or less, T 2 O 5 The content is 1.0 mass% or less, S.C. 2 O 3 The content is 2.0 mass% or less, HfO 2 The content is 1.0 mass% or less, Lu 2 O 3 The content is 2.0 mass% or less, Yb 2 O 3 The optical glass has a content of 1.0 mass % or less.

2. The optical glass according to claim 1 , which satisfies any one or more of the following: SiO 2 The content is 35% by mass or less, A 2 O 3 The content is 6.0 mass% or less, SiO 2 and Al 2 O 3 The total content [SiO 2 +Al 2 O 3 ] is 40 mass% or less, A 2 O 3 Content and SiO 2 and ZrO 2 The mass ratio of [Al 2 O 3 / (SiO 2 + ZrO 2 ) is 0.1500 or less, TiO 2 , Nb 2 O 5 , and ZrO 2 The total content of and B 2 O 3 , SiO 2 , Al 2 O 3 and GeO 2 The mass ratio of the total content of [(TiO 2 +Nb 2 O 5 + ZrO 2 ) / (B 2 O 3 +SiO 2 +Al 2 O 3 + GeO 2 ) is 1.8 or more, TiO 2 Content and Nb 2 O 5 The mass ratio of the content of [TiO 2 / Nb 2 O 5 ] is 4.0 or less.

3. The optical glass according to claim 1 , which satisfies any one or more of the following: SiO 2 The content is 25% by mass or less, A 2 O 3 The content is 3.0 mass% or less, B 2 O 3 The content is 3.0 mass% or less, Li 2 The content of O is 5.0 mass% or less, Na 2 The content of O is 3.0 mass% or less, TiO 2 The content is 14.5 mass% or more, SiO 2 and Al 2 O 3 The total content [SiO 2 +Al 2 O 3 ] is 25 mass% or less, B 2 O 3 and P 2 O 5 The total content [B 2 O 3 +P 2 O 5 ] is 0.1 mass% or more, B 2 O 3 and P 2 O 5 The total content [B 2 O 3 +P 2 O 5 ] is 3 mass% or less, Li 2 O, Na 2 O, and K 2 The total content of O [Li 2 O+Na 2 O+K 2 O] is 8.0 mass% or less, B 2 O 3 and P 2 O 5 The total content of and SiO 2 and Al 2 O 3 The mass ratio of the total content of [(B 2 O 3 +P 2 O 5 ) / (SiO 2 +Al 2 O 3 ) is 0.03 or more, A 2 O 3 Content and SiO 2 and ZrO 2 The mass ratio of [Al 2 O 3 / (SiO 2 + ZrO 2 ) is 0.1500 or less, TiO 2 and Nb 2 O 5 The total content [TiO 2 +Nb 2 O 5 ] is 33 mass% or more, TiO 2 , Nb 2 O 5 , and ZrO 2 The total content of and B 2 O 3 , SiO 2 , Al 2 O 3 and GeO 2 The mass ratio of the total content of [(TiO 2 +Nb 2 O 5 + ZrO 2 ) / (B 2 O 3 +SiO 2 +Al 2 O 3 + GeO 2 ) is 1.8 or more, TiO 2 , Nb 2 O 5 , and ZrO 2 The total content [TiO 2 +Nb 2 O 5 + ZrO 2 ] is 40 mass% or more, B 2 O 3 , ZnO, La 2 O 3 , Gd 2 O 3 , and W.O. 3 The total content of and SiO 2 , CaO, TiO 2 , and Nb 2 O 5 The total content and mass ratio [(B 2 O 3 +ZnO + La 2 O 3 +Gd 2 O 3 +W.O. 3 ) / (SiO 2 + CaO + TiO 2 +Nb 2 O 5 ) is 0.01 or more, B 2 O 3 , ZnO, La 2 O 3 , Gd 2 O 3 , and W.O. 3 The total content of and SiO 2 , CaO, TiO 2 , and Nb 2 O 5 The total content and mass ratio [(B 2 O 3 +ZnO + La 2 O 3 +Gd 2 O 3 +W.O. 3 ) / (SiO 2 + CaO + TiO 2 +Nb 2 O 5 ) is 0.19 or less, TiO 2 , CaO, SrO, and Y 2 O 3 The total content of BaO, MgO, Nb 2 O 5 , Ta 2 O 5 , W.O. 3 , Bi 2 O 3 , La 2 O 3 , and Gd 2 O 3 The mass ratio of the total content of [(TiO 2 +CaO+SrO+Y 2 O 3 ) / (BaO+MgO+Nb 2 O 5 +Ta 2 O 5 +W.O. 3 +Bi 2 O 3 +La 2 O 3 +Gd 2 O 3 ) is 0.7 or more, TiO 2 Content and Nb 2 O 5 The mass ratio of the content of [TiO 2 / Nb 2 O 5 ] is 3.0 or less, The total content of MgO, CaO, SrO, and BaO [MgO + CaO + SrO + BaO] is 18.0 mass% or more; Li 2 O, Na 2 O, and K 2 The mass ratio of the total content of O to the total content of MgO, CaO, SrO, and BaO [(Li 2 O+Na 2 O+K 2 O) / (MgO+CaO+SrO+BaO)] is 0.5 or less, Li 2 The value obtained by dividing the content of O by 29.9 and B 2 O 3 The content of Li divided by 69.6 2 The value obtained by dividing the O content by 29.9, Na 2 The value obtained by dividing the O content by 62.0, and K 2 The ratio of the total value of the content of O divided by 94.2 [(Li 2 O / 29.9) / {(B 2 O 3 / 69.6+Li 2 O / 29.9+Na 2 O / 62.0+K 2 O / 94.2)) is 0.45 or more, Li 2 The value obtained by dividing the content of O by 29.9 and B 2 O 3 The content of Li divided by 69.6 2 The value obtained by dividing the O content by 29.9, Na 2 The value obtained by dividing the O content by 62.0, and K 2 The ratio of the total value of the content of O divided by 94.2 [(Li 2 O / 29.9) / {(B 2 O 3 / 69.6+Li 2 O / 29.9+Na 2 O / 62.0+K 2 O / 94.2)) is 0.90 or less, The Abbe number νd is 30.0 or less.

4. SiO 2 The content is 5.0% by mass or more and 25.0% by mass or less, A 2 O 3 The content is 0.005% by mass or more and 3.0% by mass or less, B 2 O 3 The content is 0.4 mass% or more and 3.0 mass% or less, Li 2 The content of O is 0.5% by mass or more and 5.0% by mass or less, The CaO content is 6.0% by mass or more and 30.0% by mass or less, TiO 2 The content is 14.0 mass% or more and 40.0 mass% or less, Nb 2 O 5 2. The optical glass according to claim 1, wherein the content of is from 10.0% by mass to 35.0% by mass.

5. An optical element comprising the optical glass according to any one of claims 1 to 4.

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