Optical glass and optical element

Abstract

To provide optical glass and an optical element capable of maintaining high refractive index with reduced specific gravity and reduced raw material cost.SOLUTION: An optical glass having a SiO2 content of 5 mass% or more, a B2O3 content of 15 mass% or less, a total content of Li2O, Na2O, and K2O [Li2O+Na2O+K2O] of 1-15 mass%, a mass ratio of Li2O content to the total content of Li2O, Na2O, and K2O [Li2O / (Li2O+Na2O+K2O)] of 0.5 or less, a mass ratio of K2O content to the total content of Li2O, Na2O, and K2O [K2O / (Li2O+Na2O+K2O)] of 0.5 or less, and a mass ratio of the total content of Li2O, Na2O, and K2O to the total content of MgO, CaO, SrO, and BaO [(Li2O+Na2O+K2O) / (MgO+CaO+SrO+BaO)] of 0.6 or less.SELECTED DRAWING: None

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), MR (Mixed Reality), and VR (Virtual Reality) technologies, goggle-type or eyeglass-type display devices have been developed as AR devices, MR devices, and VR devices. For example, goggle-type display devices require lenses with a high refractive index and a low specific gravity, and there is a growing demand for glass that can be used for such lenses. However, currently, glass that can be used for such lenses uses glass components such as Nb and Li, which have high raw material costs, in order to achieve the properties of a high refractive index and a low specific gravity. As a result, the increase in raw material costs has become a problem.

[0003] Patent Document 1 discloses an optical glass with a high refractive index. However, the optical glass of Patent Document 1 has a high specific gravity relative to the refractive index, making it unsuitable for use as a lens in an AR device or the like, and contains many glass components such as Nb and Li, which have high raw material costs.

[0004] Therefore, there is a demand for optical glasses that have a reduced specific gravity while maintaining a high refractive index, thereby enabling reduction in raw material costs. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2021 / 171950 Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention has been made in view of the above circumstances, and has as its object to provide an optical glass and an optical element that maintain a high refractive index while having a reduced specific gravity and reduced raw material costs. [Means for solving the problem]

[0007] The gist of the present invention is as follows. (1) The SiO2 content is 5 mass% or more, The content of B2O3 is 15% by mass or less, the total content of LiO, NaO, and KO [LiO + NaO + KO] is 1 to 15 mass%; the mass ratio of the content of LiO to the total content of LiO, NaO, and KO [LiO / (LiO+NaO+KO)] is 0.5 or less, the mass ratio of the content of KO to the total content of LiO, NaO, and KO [KO / (LiO+NaO+KO)] is 0.5 or less; a mass ratio of the total content of LiO, NaO, and KO to the total content of MgO, CaO, SrO, and BaO [(LiO + NaO + KO) / (MgO + CaO + SrO + BaO)] is 0.6 or less; The content of TiO2 is 15 mass% or more, The content of Nb2O5 is 1 to 30 mass%; The mass ratio of the SiO2 content to the TiO2 content [SiO2 / TiO2] is 1.0 or less, The total content of MgO, CaO, SrO, and BaO [MgO + CaO + SrO + BaO] is 5% by mass or more, the mass ratio of the content of BaO to the total content of MgO, CaO, SrO, and BaO [BaO / (MgO+CaO+SrO+BaO)] is 0.7 or less; The total content of TiO2 and Nb2O5 [TiO2 + Nb2O5] is 30 mass% or more, An optical glass in which the mass ratio of the TiO2 content to the total content of TiO2, Nb2O5, Y2O3, ZrO2, La2O3, Gd2O3, Ta2O5, WO3, Yb2O3, and Bi2O3 [TiO2 / (TiO2+Nb2O5+Y2O3+ZrO2+La2O3+Gd2O3+Ta2O5+WO3+Yb2O3+Bi2O3)] is 0.6 or more.

[0008] (2) An optical element made of the optical glass described in (1) above.

[0009] (3) A light guide plate made of the optical glass described in (1) above. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide an optical glass and an optical element that maintain a high refractive index while reducing the specific gravity and the raw material costs. DETAILED DESCRIPTION OF THE INVENTION

[0011] In this invention and this specification, glass compositions are 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 exist in the glass after they are all decomposed during melting, and each glass component is conventionally expressed as SiO2, TiO2, etc. The contents and total contents of glass components are on a mass basis unless otherwise specified, and "%" means "mass%."

[0012] The content of glass components can be quantified by known methods, such as inductively coupled plasma atomic emission spectroscopy (ICP-AES), inductively coupled plasma mass spectroscopy (ICP-MS), etc. In this specification and the present invention, a content of 0% of a component means that the component is substantially not contained, and it is acceptable for the component to be present at an unavoidable impurity level.

[0013] In this specification, the thermal stability and reheating stability of glass both refer to the resistance to crystal precipitation in the glass. In particular, the thermal stability refers to the resistance to crystal precipitation when molten glass solidifies, and the reheating stability refers to the resistance to crystal precipitation when solidified glass is reheated, such as during reheat pressing.

[0014] Unless otherwise specified, the refractive index refers to the refractive index nd at the d line of helium (wavelength 587.56 nm).

[0015] The Abbe number νd is used as a value that represents the properties related to dispersion and is expressed by the following formula: where n F is the refractive index of blue hydrogen at the F line (wavelength 486.13 nm), n C is the refractive index of red hydrogen at the C line (656.27 nm). νd=(nd-1) / (n F -n C )

[0016] An embodiment of the present invention will be described below.

[0017] In the optical glass according to this embodiment, the SiO2 content is 5% or more. The lower limit of the SiO2 content is preferably 5.0%, and more preferably 6.0%, 8.0%, 10.0%, 12.0%, 14.0%, 16.0%, 17.0%, 18.0%, 19.0%, and 20.0% in that order. The upper limit of the SiO2 content is preferably 30.0%, and more preferably 29.0%, 28.0%, 27.0%, 26.0%, 25.0%, and 24.0% in that order.

[0018] SiO2 is a glass network-forming component that improves the thermal stability, chemical durability, and weather resistance of glass, and also functions to increase the viscosity of molten glass. If the SiO2 content is too low, the devitrification resistance of the glass tends to decrease. If the SiO2 content is too high, the refractive index nd may decrease.

[0019] In the optical glass according to this embodiment, the B2O3 content is 15% or less. The upper limit of the B2O3 content is preferably 15.0%, and more preferably 13.0%, 10.0%, 9.0%, 8.0%, 7.0%, 6.0%, and 5.0% in that order. The lower limit of the B2O3 content is preferably 0.0%, and more preferably 1.0%, 2.0%, and 3.0% in that order.

[0020] B2O3 improves the thermal stability of glass and enhances its meltability. Furthermore, among the glass network-forming components, it has a relatively high refractive index and can reduce specific gravity. By setting the B2O3 content within the above range, the meltability of the glass is improved, and an optical glass with a high refractive index and reduced specific gravity can be obtained. On the other hand, if the B2O3 content is too low, the high refractive index may be lost and the specific gravity may increase. Furthermore, if the B2O3 content is too high, the amount of volatilization of glass components during glass melting may increase.

[0021] In the optical glass according to this embodiment, the total content of Li2O, Na2O, and K2O [Li2O + Na2O + K2O] is 1 to 15%. The lower limit of this total content is preferably 1.0%, with 2.0%, 3.0%, and 4.0% being more preferred in that order. The upper limit of this total content is preferably 10%, with 9.0%, 8.0%, and 7.0% being more preferred in that order.

[0022] By setting the total content [Li2O + Na2O + KO] within the above range, the viscosity of the glass can be appropriately maintained and glass productivity can be improved. Furthermore, the internal transmittance at 460 nm can be increased by suppressing light absorption resulting from reducing components such as Ti and Nb, and further by lowering the melting temperature and promoting the elimination of electronic defects in the glass through slow cooling. On the other hand, if the total content is too low, the meltability of the glass raw materials deteriorates, making it necessary to set a higher melting temperature for the raw materials. If the total content is too high, the viscosity of the glass decreases, and the thermal stability associated with this decreases, which may result in a decrease in productivity. Furthermore, the resistivity of the glass melt decreases, reducing the heating efficiency when heating the glass melt by passing electricity through it, which may result in a decrease in the meltability of the glass and a decrease in productivity.

[0023] In the optical glass according to this embodiment, the mass ratio of the LiO content to the total content of LiO, NaO, and KO [LiO / (LiO + NaO + KO)] is 0.5 or less. The upper limit of this mass ratio is preferably 0.50, with 0.40, 0.30, 0.20, and 0.10 being more preferred in this order. The lower limit of this mass ratio is preferably 0.00, with 0.01 and 0.02 being more preferred in this order. By keeping this mass ratio within the above range, an optical glass with a high refractive index, a reduced specific gravity, and reduced raw material costs can be obtained.

[0024] In the optical glass according to this embodiment, the mass ratio of the K2O content to the total content of Li2O, Na2O, and K2O [K2O / (Li2O + Na2O + K2O)] is 0.5 or less. The upper limit of this mass ratio is preferably 0.40, with 0.35 and 0.30 being more preferred. The lower limit of this mass ratio is preferably 0.00, with 0.05, 0.10, and 0.15 being more preferred in that order. By keeping this mass ratio within the above range, an optical glass with a high refractive index and a reduced specific gravity can be obtained.

[0025] In the optical glass according to this embodiment, the mass ratio of the total content of Li2O, Na2O, and K2O to the total content of MgO, CaO, SrO, and BaO [(Li2O + Na2O + K2O) / (MgO + CaO + SrO + BaO)] is 0.6 or less. The upper limit of this mass ratio is preferably 0.50, with 0.45, 0.40, 0.35, and 0.30 being more preferred in that order. The lower limit of this mass ratio is preferably 0.05, with 0.10, 0.15, and 0.20 being more preferred in that order.

[0026] By setting the mass ratio [(Li2O + Na2O + KO) / (MgO + CaO + SrO + BaO)] within the above range, an optical glass with a reduced specific gravity can be obtained. Furthermore, the reduction color of the glass is suppressed, and the internal transmittance can be improved. On the other hand, if the mass ratio is too small, the meltability of the glass may deteriorate. Furthermore, if the mass ratio is too large, the glass components may be more likely to volatilize during melting, and the viscosity of the molten glass may decrease, resulting in a decrease in thermal stability.

[0027] In the optical glass according to this embodiment, the TiO2 content is 15% or more. The lower limit of the TiO2 content is preferably 20.0%, and more preferably 22.0%, 24.0%, 26.0%, and 28.0% in that order. The upper limit of the TiO2 content is preferably 60.0%, and more preferably 55.0%, 50.0%, 45.0%, 40.0%, 38.0%, and 36.0% in that order.

[0028] By setting the TiO2 content within the above range, an optical glass with a high refractive index and a reduced specific gravity can be obtained. 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.

[0029] In the optical glass according to this embodiment, the Nb2O5 content is 1 to 30%. The lower limit of the Nb2O5 content is preferably 1.0%, and more preferably 1.5%, 2.0%, 2.5%, and 3.0% in that order. The upper limit of the Nb2O5 content is preferably 20.0%, and more preferably 18.0%, 16.0%, 14.0%, 12.0%, and 10.0% in that order.

[0030] By setting the Nb2O5 content within the above range, an optical glass with a high refractive index, reduced raw material costs, and improved thermal stability can be obtained. On the other hand, if the Nb2O5 content is too low, the refractive index may decrease. If the Nb2O5 content is too high, the devitrification resistance may decrease.

[0031] In the optical glass according to this embodiment, the mass ratio of the SiO content to the TiO content [SiO / TiO] is 1.0 or less. The upper limit of this mass ratio is preferably 0.80, and more preferably 0.75, 0.70, 0.65, and 0.60, in that order. The lower limit of this mass ratio is preferably 0.20, and more preferably 0.25, 0.30, 0.35, and 0.40, in that order.

[0032] By setting the mass ratio [SiO2 / TiO2] within the above range, an optical glass with a high refractive index and a low specific gravity can be obtained, and the thermal stability and meltability of the glass can be improved.

[0033] In the optical glass according to this embodiment, the total content of MgO, CaO, SrO, and BaO [MgO + CaO + SrO + BaO] is 5% or more. The lower limit of this total content is preferably 15.0%, with 16.0%, 17.0%, and 18.0% being more preferred in that order. The upper limit of this total content is preferably 40.0%, with 38.0%, 36.0%, 34.0%, 32.0%, and 30.0% being more preferred in that order.

[0034] 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 low, the meltability of the glass may be deteriorated and the erosion of the refractory bricks during glass melting may be increased. On the other hand, if the total content is too high, the desired optical properties may not be obtained and the thermal stability may be reduced.

[0035] In the optical glass according to this embodiment, the mass ratio of the BaO content to the total content of MgO, CaO, SrO, and BaO [BaO / (MgO+CaO+SrO+BaO)] is 0.7 or less. The upper limit of this mass ratio is preferably 0.65, with 0.60, 0.55, 0.50, 0.40, 0.30, and 0.25 being more preferred in that order. The lower limit of this mass ratio is preferably 0.01, with 0.05, 0.10, and 0.15 being more preferred in that order.

[0036] By setting the mass ratio [BaO / (MgO+CaO+SrO+BaO)] within the above range, the specific gravity is reduced and an optical glass that maintains high dispersion can be obtained. If the mass ratio is too large, the specific gravity of the glass increases, which may reduce thermal stability and devitrification resistance.

[0037] In the optical glass according to this embodiment, the total content of TiO2 and Nb2O5 [TiO2 + Nb2O5] is 30% or more. The lower limit of this total content is preferably 30.0%, and more preferably 31.0%, 32.0%, 33.0%, 34.0%, and 35.0% in that order. The upper limit of this total content is preferably 60.0%, and more preferably 55.0%, 50.0%, and 45.0% in that order.

[0038] Both TiO2 and Nb2O5 are components that contribute to a high refractive index, so by keeping the total content [TiO2 + Nb2O5] within the above range, an optical glass with a high refractive index and a reduced specific gravity can be obtained.

[0039] In the optical glass according to this embodiment, the mass ratio of the TiO content to the total content of TiO, NbO, YO, ZrO, LaO, GdO, TaO, WO, YbO, and BiO [TiO / (TiO + NbO + YO + ZrO + LaO + GdO + TaO + WO + YbO + BiO)] is 0.6 or greater. The lower limit of this mass ratio is preferably 0.65, with 0.66, 0.67, and 0.68 being more preferred. The upper limit of this mass ratio is preferably 0.95, with 0.90, 0.88, 0.86, 0.84, and 0.82 being more preferred.

[0040] By setting the mass ratio [TiO2 / (TiO2+Nb2O5+Y2O3+ZrO2+La2O3+Gd2O3+Ta2O5+WO3+Yb2O3+Bi2O3)] within the above range, an optical glass with a high refractive index and a reduced specific gravity can be obtained.

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

[0042] In the optical glass according to this embodiment, the lower limit of the mass ratio of TiO2 content to Nb2O5 content [TiO2 / Nb2O5] is preferably 1.5, and more preferably 1.6, 1.7, 1.8, 1.9, and 2.0 in that order. The upper limit of this mass ratio is preferably 20.0, and more preferably 19.0, 18.0, 17.0, 16.0, and 15.0 in that order.

[0043] From the viewpoint of obtaining an optical glass with a high refractive index, a reduced specific gravity, and reduced raw material costs, it is preferable to set the mass ratio [TiO2 / Nb2O5] within the above range. On the other hand, if the mass ratio is too small, the liquidus temperature will rise, the melting property will deteriorate, and there is a risk of increased erosion of the refractory bricks during glass melting. As a result, there is a risk of increased manufacturing costs. Furthermore, if the mass ratio is too large, there is a risk of the glass's devitrification resistance being reduced and its transmittance being reduced.

[0044] In the optical glass according to this embodiment, the upper limit of the mass ratio of the NbO content to the total content of TiO, NbO, YO, ZrO, La, GdO, Ta, WO, YbO, and BiO [NbO / (TiO + NbO + YO + ZrO + La + GdO + Ta + WO + YbO + BiO)] is preferably 0.30, and more preferably 0.25 and 0.20, in that order. The lower limit of this mass ratio is preferably 0.01, and more preferably 0.02, 0.03, 0.04, and 0.05, in that order.

[0045] From the viewpoint of obtaining an optical glass having a high refractive index, a reduced specific gravity, and reduced raw material costs, it is preferable that the mass ratio [Nb2O5 / (TiO2+Nb2O5+Y2O3+ZrO2+La2O3+Gd2O3+Ta2O5+WO3+Yb2O3+Bi2O3)] be within the above range.

[0046] In the optical glass according to this embodiment, the mass ratio of the total content of TiO2, Nb2O5, YO3, ZrO2, La2O3, Gd2O3, Ta2O5, WO3, Yb2O3, and Bi2O3 to the total content of MgO, CaO, SrO, and BaO [(TiO2 + Nb2O5 + YO3 + ZrO2 + La2O3 + Gd2O3 + Ta2O5 + WO3 + Yb2O3 + Bi2O3) / (MgO + CaO + SrO + BaO)] is preferably 1.0, and more preferably 1.1, 1.2, 1.3, and 1.4 in that order. The upper limit of this mass ratio is preferably 3.0, and more preferably 2.9, 2.8, 2.7, and 2.6 in that order.

[0047] From the viewpoint of obtaining an optical glass having a high refractive index, a reduced specific gravity, and reduced raw material costs, it is preferable that the mass ratio [(TiO2+Nb2O5+Y2O3+ZrO2+La2O3+Gd2O3+Ta2O5+WO3+Yb2O3+Bi2O3) / (MgO+CaO+SrO+BaO)] be within the above range.

[0048] Both As2O3 and PbO are toxic, so in the optical glass according to this embodiment, the content of each of As2O3 and PbO is preferably 0%, and it is preferable that they are substantially absent.

[0049] In the optical glass according to this 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%. The P2O5 content may even be 0.0%.

[0050] From the viewpoint of suppressing devitrification of the glass and suppressing corrosion of the refractory bricks during glass melting, it is preferable that the content of P2O5 be within the above range.

[0051] In the optical glass according to this embodiment, the lower limit of the Al2O3 content is preferably 0.00%, and more preferably 0.01%, 0.02%, and 0.03% in that order. The upper limit of the Al2O3 content is preferably 5.0%, and more preferably 4.0%, 3.0%, 2.0%, 1.0%, and 0.5% in that order. The Al2O3 content may be 0.00%.

[0052] Al2O3 is a component that has little effect on reducing specific gravity and also has the effect of lowering refractive index. From the perspective of obtaining glass with a high refractive index and low specific gravity, the lower the Al2O3 content, the better. If the Al2O3 content is too high, the devitrification resistance of the glass may decrease, the glass transition temperature Tg may increase, and the thermal stability may decrease.

[0053] In the optical glass according to this embodiment, the lower limit of the ZrO2 content is preferably 0.01%, and more preferably 0.05%, 0.10%, 0.30%, and 0.50%, in that order. The upper limit of the ZrO2 content is preferably 20.0%, and more preferably 15.0%, 12.0%, and 10.0%, in that order.

[0054] If the ZrO2 content is too low, the corrosion of the refractory bricks may increase. If the ZrO2 content is too high, the meltability of the glass may deteriorate. From the viewpoint of obtaining an optical glass with a high refractive index while suppressing the corrosion of the refractory bricks, and from the viewpoint of maintaining the meltability and thermal stability of the glass, it is preferable that the ZrO2 content be within the above range.

[0055] In the optical glass according to this embodiment, the upper limit of the WO3 content is 10.0%, and more preferably 5.0%, 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%.

[0056] From the viewpoint of obtaining an optical glass having a reduced specific gravity and a reduced ultraviolet transmittance, it is preferable that the WO3 content be within the above range. On the other hand, if the WO3 content is too high, the internal transmittance may decrease and the specific gravity may increase. Furthermore, the transmittance in the visible range, particularly in the short wavelength range, may decrease, and the glass may become unstable.

[0057] In the optical glass according to this 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%.

[0058] From the viewpoint of obtaining an optical glass with a reduced specific gravity and reduced ultraviolet transmittance, it is preferable to set the Bi2O3 content within the above range. On the other hand, if the Bi2O3 content is too high, the specific gravity increases, and there is a risk of reducing the internal transmittance as well as the transmittance in the short wavelength range. In addition, there is a risk of increasing the amount of corrosion of platinum in the glass and increasing the coloration of the glass.

[0059] In the optical glass according to this embodiment, the upper limit of the Li2O content is preferably 5.0%, and more preferably 4.0%, 3.0%, and 2.0% in that order. The lower the Li2O content, the more preferable it is, and the lower limit is preferably 0.0%, and more preferably 0.1%, 0.5%, and 1.0% in that order. The Li2O content may even be 0.0%.

[0060] From the viewpoint of obtaining an optical glass with a high refractive index, a reduced specific gravity, and reduced raw material costs, it is preferable that the Li2O content be within the above range. Furthermore, Li2O functions to improve the meltability of the glass, reduce the resistivity of the molten glass, and suppress reduction coloration that may occur during melting of the glass. On the other hand, if the Li2O content is too high, chemical durability and weather resistance may decrease, and stability during reheating may decrease.

[0061] In the optical glass according to this embodiment, the upper limit of the NaO content is preferably 15.0%, and more preferably 12.0%, 10.0%, and 8.0% in that order. The lower limit of the NaO content is preferably 0.50%, and more preferably 1.0%, 1.5%, and 2.0% in that order.

[0062] From the viewpoint of obtaining an optical glass with a reduced specific gravity, it is preferable that the Na2O content be within the above range. Na2O also functions to improve the meltability of the glass and reduce the specific resistance of the molten glass. 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.

[0063] In the optical glass according to this embodiment, the upper limit of the K2O content is preferably 10.0%, and more preferably 8.0%, 6.0%, 5.0%, and 4.0% in that order. The lower the K2O content, the more preferable it is, and the lower limit is preferably 0.01%, and more preferably 0.05%, 0.10%, 0.30%, 0.50%, and 1.0% in that order. The K2O content may be 0.0%.

[0064] From the viewpoint of improving the meltability of the glass, it is preferable that the content of K2O is within the above range. On the other hand, if the content of K2O is too high, the refractive index may decrease significantly.

[0065] In the optical glass according to this embodiment, the upper limit of the CsO 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 CsO content is preferably 0.0%. The CsO content may be 0.0%.

[0066] Cs2O has the function of improving the meltability of glass and improving its thermal stability, but if the Cs2O content is too high, the refractive index will decrease significantly and the chemical durability of the glass may deteriorate.

[0067] In the optical glass according to this embodiment, the upper limit of the MgO content is preferably 10.0%, and more preferably 8.0%, 6.0%, 4.0%, and 2.0%, 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 even be 0.0%.

[0068] From the viewpoint of improving the stability of the glass and reducing coloration of the glass, it is preferable that the content of MgO is within the above range. On the other hand, if the content of MgO is too high, it may not be possible to achieve both a high refractive index and a low specific gravity.

[0069] In the optical glass according to this embodiment, the upper limit of the CaO content is preferably 200%, and more preferably 18.0%, 16.0%, 14.0%, 12.0%, and 10.0%, in that order. The lower limit of the CaO content is preferably 1.0%, and more preferably 2.0%, 3.0%, and 4.0%, in that order.

[0070] From the viewpoint of obtaining an optical glass with a high refractive index, a reduced specific gravity, and improved meltability, it is preferable to set the CaO content within the above range. 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. Furthermore, if the CaO content is too high, the thermal stability of the glass may decrease, and the devitrification resistance may also decrease.

[0071] In the optical glass according to this embodiment, the upper limit of the SrO content is preferably 20.0%, and more preferably 19.0%, 18.0%, 17.0%, 16.0%, and 15.0%, in that order. The lower limit of the SrO content is preferably 1.0%, and more preferably 1.5%, 2.0%, and 2.3%, in that order.

[0072] From the viewpoint of improving meltability, it is preferable that the SrO content be within the above range. 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 devitrification resistance may also decrease.

[0073] In the optical glass according to this embodiment, the upper limit of the BaO content is preferably 25.0%, and more preferably 24.0%, 23.0%, 22.0%, 21.0%, and 20.0%, in that order. The lower limit of the BaO content is preferably 0.50%, and more preferably 0.70%, 1.0%, 1.20%, and 1.50%, in that order.

[0074] From the viewpoint of improving meltability, it is preferable that the BaO content be within the above range. On the other hand, if the BaO content is too low, the stability of the glass may decrease. Also, if the BaO content is too high, the specific gravity may increase significantly, making it impossible to maintain high dispersibility, reducing the thermal stability of the glass, and reducing devitrification resistance.

[0075] In the optical glass according to this embodiment, the upper limit of the ZnO content is preferably 10.0%, and more preferably 8.0%, 6.0%, 4.0%, and 2.0%, 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 even be 0.0%.

[0076] From the viewpoint of lowering the glass transition temperature Tg, it is preferable that the ZnO content be within the above range. On the other hand, if the ZnO content is too high, the specific gravity increases and the stability of the glass may be impaired.

[0077] In the optical glass according to this 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%. The La2O3 content may be 0.0%.

[0078] From the viewpoint of obtaining an optical glass with a high refractive index without deteriorating the internal transmittance of the glass, it is preferable to set the La2O3 content within the above range. On the other hand, if the La2O3 content is low, the refractive index tends to decrease. Furthermore, if the La2O3 content is too high, the specific gravity increases, and the thermal stability of the glass may decrease.

[0079] In the optical glass according to this 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%. The Gd2O3 content may even be 0.0%.

[0080] From the viewpoint of obtaining an optical glass with a high refractive index without deteriorating the internal transmittance of the glass, it is preferable to set the Gd2O3 content within the above range. On the other hand, if the Gd2O3 content is too high, the thermal stability of the glass may decrease, the specific gravity may increase, and the manufacturing cost of the glass may increase.

[0081] In the optical glass according to this 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%.

[0082] By incorporating Y2O3 within the above range, for example, in place of ZrO2 or Nb2O5, 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 Y2O3 content is low, the refractive index tends to decrease. Furthermore, if the Y2O3 content is too high, the thermal stability of the glass may decrease, and the devitrification resistance may also decrease.

[0083] In the optical glass according to this 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. Furthermore, the lower the GeO2 content, the more preferable it is, and the lower limit is preferably 0.0%.

[0084] GeO2 is an expensive glass component, and if the GeO2 content is too high, the manufacturing cost may increase.

[0085] In the optical glass according to this 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%. The Ta2O5 content may be 0.0%.

[0086] Ta2O5 is a glass component that increases the refractive index without deteriorating the internal transmittance of the glass. However, Ta2O5 is an expensive glass component, and a high Ta2O5 content may increase raw material costs. It may also increase the specific gravity. Therefore, it is preferable that the Ta2O5 content be within the above range.

[0087] In the optical glass according to this embodiment, the Sc2O3 content is preferably 2% or less, and the lower limit of the Sc2O3 content is preferably 0%.

[0088] In the optical glass according to this embodiment, the content of HfO2 is preferably 2% or less, and the lower limit of the content of HfO2 is preferably 0%.

[0089] Sc2O3 and HfO2 have the effect of increasing the refractive index of the glass, but are expensive components, so it is preferable that the contents of Sc2O3 and HfO2 are each within the above ranges.

[0090] In the optical glass according to this embodiment, the content of Lu2O3 is preferably 2% or less, and the lower limit of the content of Lu2O3 is preferably 0%.

[0091] 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.

[0092] In the optical glass according to this embodiment, the Yb2O3 content is preferably 2% or less, more preferably 1% or less, and even more preferably 0.5% or less. The lower limit of the Yb2O3 content is preferably 0%. The Yb2O3 content may be 0.0%.

[0093] Yb2O3 functions to adjust the refractive index of the glass, but because of its large molecular weight, it increases the specific gravity of the glass. An increase in the specific gravity of the glass increases the mass of the optical element. Therefore, it is desirable to reduce the Yb2O3 content to prevent the increase in the specific gravity of the glass.

[0094] Furthermore, if the Yb2O3 content is too high, the thermal stability of the glass decreases. Furthermore, it causes absorption in the infrared region. From the viewpoint of preventing a decrease in the thermal stability of the glass and suppressing an increase in specific gravity, the Yb2O3 content is preferably within the above range.

[0095] The optical glass according to this embodiment is preferably composed primarily of the above-mentioned glass components, namely, SiO2, TiO2, and Nb2O5 as essential components, and B2O3, P2O5, Al2O3, ZrO2, WO3, Bi2O3, Li2O, Na2O, K2O, Cs2O, MgO, CaO, SrO, BaO, ZnO, La2O3, Gd2O3, Y2O3, GeO2, Ta2O5, Sc2O3, HfO2, Lu2O3, and Yb2O3 as optional components, 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.

[0096] The optical glass according to this 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.

[0097] (Other ingredients) 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.

[0098] U, Th, and Ra are all radioactive elements, so it is preferable that the optical glass according to this embodiment does not contain these elements as glass components.

[0099] V, Cr, Mn, Fe, Co, Ni, Cu, Pr, Nd, Pm, Sm, Eu, Tb, Dy, Ho, Er, and Tm can increase the coloration of the glass and become a source of fluorescence. Therefore, the optical glass according to this embodiment can contain trace amounts of these elements as glass components within a range that does not impair the function of the optical glass. In effect It is preferable that it is not contained.

[0100] Sb2O3 and CeO2 are elements that can be added as desired and function as fining agents. Of these, Sb2O3 is a fining agent with a strong fining effect. CeO2 has a weaker fining effect than Sb2O3. Adding a large amount of CeO2 tends to intensify the coloring of the glass.

[0101] The Sb2O3 content is expressed as an exclusive percentage. That is, when the total content of all glass components other than Sb2O3 and CeO2 is taken as 100 mass%, the Sb2O3 content 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 Sb2O3 content may be 0 mass%.

[0102] The CeO2 content is also expressed as an exclusive percentage. 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, even more preferably 0.5 mass% or less, and even more preferably 0.1 mass% or less. The CeO2 content may be 0 mass%. By keeping the CeO2 content within the above range, the clarity of the glass can be improved.

[0103] (Glass characteristics) <Refractive index nd> In the optical glass according to this embodiment, the upper limit of the refractive index nd can be 2.00, or even 1.99, 1.98, 1.97, 1.96, or 1.95. The lower limit of the refractive index nd can be 1.82, or even 1.83, 1.84, or 1.85. 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, or YO3; adjusting the content of low-refractive-index components, such as SiO2, Al2O3, or BO3; or by incorporating a modifying component, such as CaO.

[0104] <Abbe number νd> In the optical glass according to this embodiment, the upper limit of the Abbe number νd can be 30.0, or even 29.0, 28.0, 27.0, 26.0, 25.0, or 24.0. The lower limit of the Abbe number νd can be 15.0, or even 16.0, 17.0, 18.0, 19.0, 20.0, 21.0, or 22.0. By setting the Abbe number νd within the above range, a glass having the desired dispersion 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.

[0105] <Specific gravity of glass> The optical glass according to this 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, thermal stability will be reduced.

[0106] Therefore, in the optical glass according to this 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 2.8, 3.0, and 3.2 in that order.

[0107] The specific gravity of a glass is determined by the atomic weight of the constituent elements and the volume occupied by those atoms. For example, the introduction of oxides containing sixth-period elements or elements with a large atomic number (57 or higher) tends to increase the specific gravity, but if the volume occupied by those elements is also large, the increase in specific gravity can be suppressed. However, if the volume occupied by an element is too large, the refractive index decreases. Furthermore, the volume occupied by an element is not specific and can change slightly depending on the presence of other glass components. In this way, the specific gravity can be controlled by adjusting the total amount and ratio of each component. Furthermore, the volume occupied by each element can change slightly depending on the annealing conditions of the glass.

[0108] <Glass transition temperature Tg> In the optical glass according to this embodiment, there is no particular upper limit to the glass transition temperature Tg, but in consideration of productivity, such as the time required for slow cooling, it is preferably 850°C, with 800°C, 750°C, and 700°C being more preferred in that order. There is no particular lower limit to the glass transition temperature Tg, but from the viewpoint of providing the optical glass with adequate heat resistance, it is preferably 100°C, with 200°C, 300°C, 400°C, and 500°C being more preferred in that order. The glass transition temperature Tg is controlled by increasing or decreasing the amount of network-forming components of the glass, adjusting the ratio of each component, etc.

[0109] By ensuring that the upper limit of the glass transition temperature Tg satisfies the above range, increases in the molding temperature and annealing temperature during glass reheat pressing can be suppressed, and thermal damage to the reheat press molding equipment and annealing equipment can be reduced.

[0110] 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.

[0111] <Glass coloring> In the optical glass according to this embodiment, light transmittance can be evaluated by the coloring intensities λ80, λ70, and λ5. For a glass sample having a thickness of 10.0 mm±0.1 mm, the spectral transmittance is measured in the wavelength range of 200 to 700 nm, and the wavelength at which the external transmittance is 80% is defined as λ80, the wavelength at which the external transmittance is 70%, and the wavelength at which the external transmittance is 5% is defined as λ70, the wavelength at which the external transmittance is 70%, and the wavelength at which the external transmittance is 5%. The upper limit of λ80 in the optical glass according to this embodiment is preferably 690 nm, and may even be 685 nm or 680 nm. The upper limit of λ70 is preferably 680 nm, and may even be 670 nm or 660 nm. The upper limit of λ5 is preferably 400 nm, and may even be 395 nm or 390 nm.

[0112] (Optical glass manufacturing) The optical glass according to this embodiment may be produced by blending glass raw materials to obtain the predetermined composition and then using the blended glass raw materials in accordance with a known glass manufacturing method. For example, multiple compounds may be blended and thoroughly mixed to form a batch raw material. The batch raw material is then placed in a crucible made of refractory bricks, heated to form a glass melt, and then refined and homogenized. The glass melt is then formed and slowly cooled to obtain the optical glass. The refining and homogenization steps may also be carried out in a platinum crucible. When melting in a platinum crucible, melting may also be carried out in a non-oxidizing atmosphere, such as a nitrogen atmosphere or a water vapor atmosphere, to suppress oxidation of platinum. Known methods may be used to form and slowly cool the glass melt. Cullet obtained by rapidly cooling a glass melt roughly melted in a refractory brick or quartz crucible may also be used as the glass raw material.

[0113] The compounds used when preparing the batch raw materials are not particularly limited as long as they can introduce desired glass components into the glass to achieve desired contents. Examples of such compounds include oxides, carbonates, nitrates, hydroxides, hydrates, fluorides, chlorides, and the like.

[0114] (Manufacturing of optical elements, etc.) To produce an optical element using the optical glass according to an embodiment of the present invention, a known method may be applied. For example, in the production of the optical glass, molten glass is poured into a mold and formed into a plate to produce a glass material made of the optical glass according to the present invention. The obtained glass material is appropriately cut, ground, and polished to produce cut pieces of a size and shape suitable for press molding. The cut pieces are heated and softened, and press-molded (reheat pressed) using a known method to produce an optical element blank that approximates the shape of the optical element. The optical element blank is annealed, and then ground and polished using a known method to produce an optical element.

[0115] The optically functional surface of the fabricated optical element may be coated with an anti-reflection film, a total reflection film, or the like depending on the intended use.

[0116] According to one aspect of the present invention, an optical element made of the above optical glass can be provided. Examples of the types of optical elements include lenses such as flat lenses, spherical lenses, and aspherical lenses, as well as prisms, diffraction gratings, and light guide plates. Examples of the lens shapes include biconvex lenses, plano-convex lenses, biconcave lenses, plano-concave lenses, convex meniscus lenses, and concave meniscus lenses.

[0117] Optical elements can be produced by a method including a step of processing a glass molded body made of the above-mentioned optical glass. Examples of processing include cutting, milling, rough grinding, fine grinding, polishing, etc. By using the above-mentioned glass, breakage can be reduced and high-quality optical elements can be steadily supplied.

[0118] The light guide plate can be fabricated by a known method using the optical glass. Examples of applications of the light guide plate include display devices such as eyeglass-type devices for augmented reality (AR), mixed reality (MR), or virtual reality (VR). Such a light guide plate is a plate-shaped glass attached to the frame of an eyeglass-type device and is made of the optical glass. If necessary, a diffraction grating may be formed on the surface of the light guide plate to change the direction of light propagating through the interior of the light guide plate by repeated total reflection. The diffraction grating can be formed by a known method. When an eyeglass-type device having the light guide plate is worn, light propagating through the interior of the light guide plate enters the pupil, thereby exhibiting the function of augmented reality (AR), mixed reality (MR), or virtual reality (VR). Such eyeglass-type devices are disclosed, for example, in JP 2017-534352.

[0119] Optical elements, particularly lenses and light guide plates, can be made less susceptible to breakage by chemically strengthening the glass during the manufacturing process. Chemical strengthening can be achieved by applying known methods. [Example]

[0120] 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.

[0121] Example 1 Glass samples having the glass compositions shown in Tables 1(1) to (4), 2(1) to (4), and 3(1) to (4) were prepared by the following procedure and subjected to various evaluations. No. 64 is a comparative example.

[0122] [Optical glass manufacturing] Oxides, hydroxides, carbonates, and nitrates corresponding to the glass constituents were prepared as raw materials. These raw materials were weighed and mixed so that the resulting optical glass had the glass composition shown in Table 1 (1) to (4). The raw materials were then thoroughly mixed. The resulting blended raw materials (batch raw materials) were placed in a crucible made of refractory oxide and heated at 1150°C to 1450°C for 1 hour to form a molten glass. The resulting mixture was then transferred to a platinum crucible, stirred to homogenize, and clarified. The molten glass was then cast into a mold preheated to an appropriate temperature. Alternatively, the blended raw materials were placed in a platinum crucible, heated for 2 hours, and then cast into a mold using the same procedure. The cast glass was heat-treated for 30 minutes at a temperature near the glass transition temperature (Tg) or approximately 10 to 100°C lower than Tg, and then allowed to cool to room temperature in the furnace to obtain a glass sample.

[0123] [Confirmation of glass composition] The content of each glass component in the obtained glass sample was measured by inductively coupled plasma atomic emission spectroscopy (ICP-AES), and it was confirmed that each composition was as shown in Table 1 (1) to (4).

[0124] [Optical property measurement] The obtained glass sample was further annealed at a temperature near the glass transition temperature Tg for about 30 minutes to about 2 hours, and then cooled to room temperature in a furnace at a rate of -30°C / hour to obtain an annealed sample. The refractive indices nd, ng, and n F and n CThe Abbe number νd, specific gravity, glass transition temperature Tg, and coloring intensities λ80, λ70, and λ5 were measured. The results are shown in Tables 4(1) to 4(4). (i) Refractive indexes nd, ng, and n F , n C and Abbe number νd The refractive indices nd, ng, and n of the above annealed sample were measured using the refractive index measurement method of JIS B 7071-1. F , n C was measured, and the Abbe number νd was calculated based on the following formula. νd=(nd-1) / (n F -n C )

[0125] (ii) Specific gravity The specific gravity was measured by the Archimedes method.

[0126] (iii) Glass transition temperature Tg The glass transition temperature Tg was measured using a differential scanning calorimeter (DSC3300SA) manufactured by NETZSCH JAPAN at a temperature rise rate of 10°C / min.

[0127] (iv) Coloring degree λ80, λ70, λ5 The above sample was processed to a thickness of 10 mm so that it had parallel, optically polished flat surfaces, and its spectral transmittance was measured in the wavelength range from 280 nm to 700 nm. The intensity of the light beam incident perpendicularly on one of the optically polished flat surfaces was defined as intensity A, and the intensity of the light beam emerging from the other flat surface was defined as intensity B, and the spectral transmittance B / A was calculated. The wavelength at which the spectral transmittance was 80% was defined as λ80, the wavelength at which the spectral transmittance was 70% was defined as λ70, and the wavelength at which the spectral transmittance was 5% was defined as λ5. Note that the spectral transmittance also includes the reflection loss of the light beam on the sample surface.

[0128] [Table 1(1)]

[0129] [Table 1(2)]

[0130]

Table 1(3)

[0131]

Table 1(4)

[0132]

Table 2(1)

[0133]

Table 2(2)

[0134]

Table 2(3)

[0135]

Table 2(4)

[0136]

Table 3(1)

[0137]

Table 3(2)

[0138]

Table 3(3)

[0139]

Table 3(4)

[0140] [Table 4(1)]

[0141] [Table 4(2)]

[0142] [Table 4(3)]

[0143] [Table 4(4)]

[0144] Example 2 Lens blanks were prepared by known methods using the optical glasses prepared in Example 1, and the lens blanks were processed by known methods such as polishing to prepare various lenses.

[0145] The optical lenses produced include various lenses such as flat lenses, biconvex lenses, biconcave lenses, plano-convex lenses, plano-concave lenses, concave meniscus lenses, and convex meniscus lenses. Here, the optical glass can also be cut without being softened by heating to obtain a lens blank. Prisms were also produced by known methods using the optical glasses produced in Example 1.

[0146] Furthermore, using each of the optical glasses produced in Example 1, a light guide plate for use in an augmented reality display device such as a wearable display was produced by a known method.

[0147] Because the glass has a low specific gravity, the light guide plate produced was lighter than light guide plates with similar optical properties and size, making it suitable as a light guide plate for use in augmented reality display devices such as wearable displays.

[0148] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims.

[0149] For example, by adjusting the composition as described in the specification for 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. SiO 2 The content of is 5% by mass or more, B 2 O 3 The content of is 15% by 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 1 to 15 mass %, Li 2 O, Na 2 O, and K 2 Li relative to the total content of O 2 Mass ratio of the content of O [Li 2 O / (Li 2 O + Na 2 O+K 2 O)] is 0.5 or less, Li 2 O, Na 2 O, and K 2 K relative to the total content of O 2 Mass ratio of the content of O [K 2 O / (Li 2 O + Na 2 O+K 2 O)] is 0.5 or less, Li relative to the total content of MgO, CaO, SrO, and BaO 2 O, Na 2 O, and K 2 Mass ratio of the total content of O [(Li 2 O + Na 2 O+K 2 O) / (MgO+CaO+SrO+BaO)] is 0.6 or less, TiO 2 The content of is 15% by mass or more, Nb 2 O 5 The content is 1 to 30 mass %, TiO 2 SiO content 2 The mass ratio of the content [SiO 2 / TiO 2 ] is 1.0 or less, the total content of MgO, CaO, SrO, and BaO [MgO + CaO + SrO + BaO] is 5% by mass or more; a mass ratio of the content of BaO to the total content of MgO, CaO, SrO, and BaO [BaO / (MgO+CaO+SrO+BaO)] is 0.7 or less; TiO 2 and Nb 2 O 5 The total content [TiO 2 +Nb 2 O 5 ] is 30% by mass or more, TiO 2 , Nb 2 O 5 , Y 2 O 3 , ZrO 2 , La 2 O 3 , Gd 2 O 3 , Ta 2 O 5 , W.O. 3 , Yb 2 O 3 , and Bi 2 O 3 TiO relative to the total content 2 The mass ratio of the content [TiO 2 / (TiO 2 +Nb 2 O 5 +Y 2 O 3 + ZrO 2 +La 2 O 3 +Gd 2 O 3 +Ta 2 O 5 +WO 3 +Yb 2 O 3 +Bi 2 O 3 ) ] is 0.6 or more.

2. An optical element made of the optical glass according to claim 1.

3. A light guide plate made of the optical glass according to claim 1.

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