TW202132234A - Optical glass and optical element - Google Patents

Abstract

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

Description

Optical glass and optical components

The present invention relates to optical glass and optical elements.

In recent years, with the advancement of AR (Amplified Reality) technology, as AR devices, display devices such as goggles and glasses have been developed. For example, in goggles-type display devices, flat lenses are used, but lenses with high refractive index, high transmittance, and low specific gravity, and the demand for glass suitable for such lenses is increasing. The transmittance here refers to the internal transmittance when light penetrates the inside of the glass, which is different from the external transmittance including reflection loss.

Generally, the refractive index of glass, the greater the interaction between the light penetrating the glass and the electron cloud in the glass, the higher. Therefore, in order to increase the refractive index of the glass, the glass composition is selected so that more electrons are filled in the glass. That is, a glass component that has a large atomic order but a small ion radius and contains many electrons is selected to increase the electron density per unit volume equivalent of the glass (mostly the oxygen number density). As an example, a boric acid-lanthanum series glass can be mentioned. However, the boric acid-lanthanum series glass has a high specific gravity, and it is a problem that the lens becomes heavier when used in a goggle-type AR display device.

As a glass component that maintains a low specific gravity and increases the refractive index, Nb ₂ O ₅ or TiO ₂ having absorption in the near ultraviolet region can be cited. However, increasing the content of such a glass component has a problem that the light absorption region not only extends to the near ultraviolet region but also extends to the visible short wavelength region (blue region). In addition, _{if the content of Nb 2} O ₅ or TiO ₂ is increased, the proportion of other ions that can supply oxygen to Nb ions or Ti ions will be relatively reduced, and part of Nb ions or Ti ions will be reduced and colored, which will reduce the glass The problem of internal transmittance of visible light.

In addition, one of the main reasons for the decrease in glass transmittance is the incorporation of platinum (Pt) from the glass melting furnace. For example, in order to increase the refractive index of glass and increase _{the content of Nb 2} O ₅ or TiO ₂ , the melting temperature of the glass rises, and it is necessary to heat the glass raw material at a high temperature. At this time, the high-temperature molten glass is in contact with platinum (Pt), and the Pt ions are dissolved in the molten glass and solid-dissolved in the glass. Pt has absorption in the ultraviolet region, but when the amount of Pt in the glass increases, the light absorption region is not only the ultraviolet region, but also extends to the visible light region. As a result, the internal transmittance of the glass in the visible light region will be reduced.

On the other hand, it is possible to melt glass in a melting furnace using refractory bricks to suppress the incorporation of platinum (Pt) originating from the melting furnace. Examples of the glass that can be melted in a melting furnace using refractory bricks include SiO ₂ -TiO ₂ glass. This type of glass is known to increase the refractive index nd to about 1.85, and to lower the specific gravity to about 3.5, and the transmittance is relatively excellent (Patent Document 1).

Here, the refractory brick _{is a brick containing ZrO 2} or Al ₂ O ₃ and/or SiO ₂ as a main component (for example, Patent Document 2). The content ratio of each component is, for example, ZrO ₂ :Al ₂ O ₃ :SiO ₂ =4:5:1, or 3:6:1, such as https://www.an.shimadzu.co.jp/apl As shown in /material/chem0502005.htm, there are also refractory bricks that _{do not substantially contain Al 2} O ₃ and SiO _2. However, as in Patent Document 2, in order to improve the thermal shock resistance or corrosion resistance, a certain amount of Al ₂ O ₃ is often contained.

However, to be applied to the lens of an AR display device, the refractive index needs to be further increased. _{For example, Patent Document 3 discloses a SiO 2} -TiO ₂ system 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, the melting temperature of this glass is high, which corrodes the vitreous part of the refractory brick of the melting furnace, and as a result, there is a problem that the components of the refractory brick are easily mixed into the glass. In glass, components derived from refractory bricks are solid-solved, especially when a large amount of ZrO ₂ component or SiO ₂ component is solid-solved in glass, the glass composition changes, and it is difficult to maintain the stability of the glass or maintain a high refractive index. In addition, the main components of the refractory bricks, such as Al ₂ O ₃ or ZrO ₂ , are mixed into the glass with foreign substances, which may impair the homogeneity of the glass. Therefore, such glass needs to be melted in a platinum container, but when the glass is melted in a platinum container, Pt is introduced into the glass as described above, and there is a problem that the internal transmittance is lowered.

With SiO ₂ glass containing Nb ₂ O ₅ or TiO ₂ , the glass melted in a melting furnace using refractory bricks can maintain a high refractive index to increase the transmittance. Such glass, there are lenses used in AR display devices. [Prior Art Document] [Patent Document]

[Patent Document 1] Japanese Patent No. 2535407 [Patent Document 2] Japanese Special Form No. 2018-537387 [Patent Document 3] JP 2012-229135 A

[Problems to be solved by the invention]

The present invention has been completed in view of this fact, and aims to provide optical glass and optical elements with high internal transmittance at a wavelength of 460 nm and high refractive index. [Means for solving problems]

The gist of the present invention is as follows. (1) An optical glass, the mass ratio of the total content of _{BaO, La 2} O ₃ , Gd ₂ O ₃ and WO _{3 to} the total content of CaO, SrO and Y ₂ O _{3 [(BaO+La 2} O ₃ +Gd ₂ O ₃ +WO ₃ )/(CaO+SrO+Y ₂ O ₃ )] is 2.0 or less, the mass ratio of the total content of _{B 2} O ₃ and P ₂ O _{5 to} the total content of SiO ₂ and Al ₂ O _{3 [} (B ₂ O ₃ +P ₂ O ₅ )/(SiO ₂ +Al ₂ O ₃ )] is 0.10 or less, the total content of _{Li 2} O, Na ₂ O, and K _{2 O [Li 2} O+Na ₂ O+K ₂ O] 10 mass% or less, Al ₂ O ₃ mass content and the total content of SiO ₂ and ZrO ₂ ratio _{[(Al 2 O 3 / (} SiO 2 + ZrO 2)] is greater than 0.0000.

(2) An optical glass in which the total content of _{TiO 2} and Nb ₂ O _{5 [TiO 2} +Nb ₂ O ₅ ] is 20% by mass or more, and the mass of the content of _{Al 2} O ₃ and the total content of SiO ₂ and ZrO ₂ The ratio [(Al ₂ O ₃ /(SiO ₂ +ZrO ₂ )] is greater than 0.0000.

(3) The optical glass as in (2), wherein the mass ratio of the total content of _{B 2} O ₃ and P ₂ O _{5 to} the total content of SiO ₂ and Al ₂ O _{3 [(B 2} O ₃ +P ₂ O ₅ ) /(SiO ₂ +Al ₂ O ₃ )] is 0.15 or less.

(4) The optical glass as in (2) or (3), wherein _{the total content of TiO 2} , Nb ₂ O ₅ and ZrO _{2 and} the total content of B ₂ O ₃ , SiO ₂ , Al ₂ O ₃ and GeO ₂ The ratio [(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, BaO, La ₂ O ₃ , Gd ₂ O ₃ and WO The mass ratio of the total content of _{3 to} the total content of CaO, SrO and Y ₂ O _{3 [(BaO+La 2} O ₃ +Gd ₂ O ₃ +WO ₃ )/(CaO+SrO+Y ₂ O ₃ ) is 3.0 or less .

(5) The optical glass of any one of (2) to (4), in which _{the total content of TiO 2} , Nb ₂ O ₅ and ZrO ₂ is equal to that of B ₂ O ₃ , SiO ₂ , Al ₂ O ₃ and GeO ₂ The mass ratio of the total content [(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, B ₂ O ₃ , ZnO, La ₂ The mass ratio of the total content of O ₃ , Gd ₂ O ₃ and WO _{3 to} the total content of SiO ₂ , CaO, TiO ₂ and Nb ₂ O _{5 [(B 2} O ₃ +ZnO+La ₂ O ₃ +Gd ₂ O ₃ +WO ₃ )/(SiO ₂ +CaO+TiO ₂ +Nb ₂ O ₅ )] is 0.15 or less.

(6) An optical element composed of the optical glass of any one of (1) to (5). [Effects of Invention]

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.

Hereinafter, one aspect of the present invention will be explained. Furthermore, in the present invention and this specification, the glass composition, unless otherwise mentioned, is expressed on an oxide basis. The so-called "oxide-based glass composition" here refers to the glass composition obtained by decomposing the glass raw materials during melting and converting to the presence of oxides in the glass. The description of each glass component follows conventions and is described as SiO ₂ , TiO ₂ and so on. If the content and total content of the glass components are not specifically mentioned as a quality standard, "%" means "mass%".

The content of the glass component can be quantified by conventional methods, such as inductively coupled plasma emission spectrometry (ICP-AES), inductively coupled plasma mass spectrometry (ICP-MS) and other methods. In addition, in this specification and the present invention, the content of a constituent component of 0% means that it is not substantially contained in the constituent component, and it is allowed to contain the component at an unavoidable impurity level.

Hereinafter, the optical glass of the present invention is divided into a first embodiment and a second embodiment. In addition, the action and effect of each glass component in the second embodiment are the same as the action and effect of each glass component in the first embodiment. Therefore, in the second embodiment, matters overlapping with the description of the first embodiment will be omitted as appropriate.

Embodiment 1 Regarding the optical glass of Embodiment 1, the mass ratio of the total content of _{BaO, La 2} O ₃ , Gd ₂ O ₃ and WO _{3 to} the total content of CaO, SrO, and Y ₂ O _{3 [(BaO+} La ₂ O ₃ +Gd ₂ O ₃ +WO ₃ )/(CaO+SrO+Y ₂ O ₃ )] is 2.0 or less, _{the total content of B 2} O ₃ and P ₂ O _{5 is} the same as that of SiO ₂ and Al ₂ O ₃ The mass ratio of the total content [(B ₂ O ₃ +P ₂ O ₅ )/(SiO ₂ +Al ₂ O ₃ )] is 0.10 or less, and the total content of _{Li 2} O, Na ₂ O, and K _{2 O [Li 2} O _{+ Na 2 O + K 2 O} ] 10 mass% or less, and the mass content of Al ₂ O ₃ and SiO ₂ and ZrO total content ₂ ratio _{[(Al 2 O 3 / (} SiO 2 + ZrO 2)] is greater than 0.0000 .

In the optical glass of the first embodiment, the mass ratio of the total content of _{BaO, La 2} O ₃ , Gd ₂ O ₃ and WO _{3 to} the total content of CaO, SrO, and Y ₂ O _{3 [(BaO+La 2} O ₃ +Gd ₂ O ₃ +WO ₃ )/(CaO+SrO+Y ₂ O ₃ )] is 2.0 or less. The upper limit of the mass ratio is preferably 1.9, and more preferably 1.8, 1.7, and 1.6 in order. The lower limit of the mass ratio is preferably 0.0, and further preferably 0.3, 0.5, 0.8, 1.0, 1.2 in order.

By setting the mass ratio [(BaO+La ₂ O ₃ +Gd ₂ O ₃ +WO ₃ )/(CaO+SrO+Y ₂ O ₃ )] within the above range, high refractive index components with excessive atomic weight can be suppressed, especially The content of elements that have the effect of relatively increasing the refractive index after the sixth period element, or restricting the use amount of high refractive index components that promote oxygen filling, can reduce the specific gravity of the glass. On the other hand, if the mass ratio is too large, the dynamic viscosity of the molten glass will decrease due to the increase in the specific gravity of the glass, making it difficult to control the flow of the glass, etc., which may deteriorate productivity. In addition, there is a risk of increasing the corrosion of refractory bricks.

In the optical glass of the first embodiment, the mass ratio of the total content of _{B 2} O ₃ and P ₂ O _{5 to} the total content of SiO ₂ and Al ₂ O _{3 [(B 2} O ₃ +P ₂ O ₅ )/( SiO ₂ +Al ₂ O ₃ )] is 0.10 or less. The upper limit of the mass ratio is preferably 0.09, and more preferably 0.08, 0.07, and 0.06 in this order. In addition, 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 order.

By setting the mass ratio [(B ₂ O ₃ +P ₂ O ₅ )/(SiO ₂ +Al ₂ O ₃ )] within the above range, it is possible to suppress the corrosion of the glass of the refractory brick during glass melting. If the mass ratio is too large, the corrosion of the refractory bricks will increase, which may reduce the homogeneity of the molten glass and reduce the devitrification resistance.

In the optical glass of the first embodiment, the total content of _{Li 2} O, Na ₂ O, and K _{2 O [Li 2} O+Na ₂ O+K ₂ O] is 10% or less. The upper limit of the total content is preferably 8.0%, and more preferably 6.0%, 5.0%, and 4.0% in this order. In addition, the lower limit of the total content is preferably 0.01%, and more preferably 0.5%, 1.0%, 1.5%, 2.0%, and 3.0% in order.

By setting the total content [Li ₂ O+Na ₂ O+K ₂ O] within the above range, the viscosity of the glass can be appropriately maintained and the productivity of the glass can be improved. In addition, it suppresses the light absorption from the reducing components produced by Ti or Nb, and furthermore, by reducing the melting temperature or slow cooling to promote the elimination of electronic defects in the glass, the internal transmittance of 460nm can be improved. In addition, the corrosion of refractory bricks when the glass is melted can be suppressed. On the other hand, if the total content is too small, the meltability of the glass raw material will deteriorate, and the melting temperature of the raw material must be set high. As a result, the deterioration of the refractory bricks is promoted, and the productivity is deteriorated. Conversely, if the total content is too large, the viscosity of the glass will decrease, and consequently the thermal stability will decrease, which may deteriorate productivity. In addition, the specific resistance of the molten glass decreases, and the heating efficiency when the molten glass is heated by energization is lowered. As a result, the meltability of the glass is lowered, and there is a possibility that productivity may deteriorate.

In the optical glass on a first embodiment, the content of Al ₂ O ₃ and the mass SiO ₂ and ZrO total content ₂ ratio _{[(Al 2 O 3 / (} SiO 2 + ZrO 2)] is greater than 0.0000. The mass ratio of The lower limit is preferably 0.0001, and more preferably 0.0003, 0.0006, 0.0010, 0.0020, 0.0030, 0.0040, 0.0050, 0.0060 in order. The upper limit of the mass ratio is preferably 0.3000, and further 0.2000, 0.1500, 0.1000 in order , 0.0500, 0.0300, 0.0150 are more preferable.

By setting the mass ratio [(Al ₂ O ₃ /(SiO ₂ +ZrO ₂ )] in the above range, the corrosion of the refractory bricks during glass melting can be suppressed. In addition, this ratio is improved compared to glass outside the above range Thermal stability, devitrification during heating, or the effect of delaying crystallization when cooling molten glass. On the other hand, if the mass ratio is too large, not only the refractive index nd will be reduced, but the thermal stability will also be reduced, resulting in devitrification The fear.

Hereinafter, a preferable aspect of the optical glass of the first embodiment will be described.

Regarding the optical glass of the first embodiment, the lower limit of the total content of _{TiO 2} and Nb ₂ O _{5 [TiO 2} +Nb ₂ O ₅ ] is preferably 20%, and is further followed by 24%, 28%, 33% , 37%, 40%, 42% are better. In addition, the upper limit of the total content is preferably 70%, and more preferably 60%, 55%, 50%, and 46% in order.

TiO ₂ and Nb ₂ O _{5 are components} that hardly increase specific gravity and contribute to a higher refractive index. Therefore, in order to obtain glass having a desired refractive index without excessively increasing the specific gravity of the glass, _{the total content of TiO 2} and Nb ₂ O ₅ is preferably within the above-mentioned range.

In the optical glass of the first embodiment, the mass ratio of the total content of _{TiO 2} , Nb ₂ O ₅ and ZrO _{2 to} the total content of B ₂ O ₃ , SiO ₂ , Al ₂ O ₃ and GeO _{2 [(TiO 2} + The lower limit of Nb ₂ O ₅ +ZrO ₂ )/(B ₂ O ₃ +SiO ₂ +Al ₂ O ₃ +GeO ₂ )] is preferably 1.8, and further preferably 2.0, 2.1, 2.2, 2.3 in order. In addition, the upper limit of the mass ratio is preferably 7.0, and more preferably 6.0, 5.0, 4.0, 3.5, and 3.0 in this order.

By setting the mass ratio [(TiO ₂ +Nb ₂ O ₅ +ZrO ₂ )/(B ₂ O ₃ +SiO ₂ +Al ₂ O ₃ +GeO ₂ )] in the above range, the refractive index can be increased and used as AR When the display device lens of the device is used, a wide viewing angle can be realized. In addition, optical glass with a further reduced specific gravity can be obtained. On the other hand, if the mass ratio is too small, the refractive index of the contrast will decrease, so it is not suitable for the application of the present invention. In addition, if the mass ratio is too large, in addition to reducing the stability of the glass, it may also reduce the transmittance.

In the optical glass of the first embodiment, _{the total content of B 2} O ₃ , ZnO, La ₂ O ₃ , Gd ₂ O ₃ and WO _{3 and} the total content of SiO ₂ , CaO, TiO ₂ and Nb ₂ O ₅ The upper limit of the mass ratio [(B ₂ O ₃ +ZnO+La ₂ O ₃ +Gd ₂ O ₃ +WO ₃ )/(SiO ₂ +CaO+TiO ₂ +Nb ₂ O ₅ )] is preferably 0.15, and further in order It is more preferably 0.12, 0.10, 0.08. In addition, the lower limit of the mass ratio is preferably 0.01, and more preferably 0.02, 0.03, 0.04, 0.05, and 0.06 in order.

By setting the mass ratio [(B ₂ O ₃ +ZnO+La ₂ O ₃ +Gd ₂ O ₃ +WO ₃ )/(SiO ₂ +CaO+TiO ₂ +Nb ₂ O ₅ )] in the above range, it is possible to suppress more The content rate of the glass component contained in the glass of the type generally using boric acid as the network forming agent, as a result, can suppress the corrosion of the refractory brick when the glass is melted. As a result, the glass can be prevented from contacting with platinum and the internal transmittance of the glass can be improved. In addition, by making the mass ratio within the above-mentioned range, it also restricts the amount of components with excessive atomic weight, or restricts the use of high-refractive-index components that promote oxygen filling, etc., so the specific gravity is lowered with the same refractive index, and the glass is suppressed by The dynamic viscosity is reduced and the productivity can be improved.

Regarding the optical glass of the first embodiment, _{the lower limit of the content of Al 2} O ₃ is preferably 0.001%, and further, in this order, 0.002%, 0.003%, 0.005%, 0.007%, 0.010%, 0.025%, 0.050%, 0.075%, 0.100%, 0.125%, 0.150%, 0.175%, 0.200% are more preferable. The upper limit of the content of Al ₂ O ₃ is preferably 10.0%, and more preferably 6.0%, 3.0%, 1.00%, and 0.50% in this order.

When melting glass using a refractory brick melting furnace, Al ₂ O ₃ from the refractory brick is introduced into the molten glass. Therefore, even when the glass raw material does not contain Al ₂ O ₃ , the glass produced by melting in a melting furnace using refractory bricks contains a small amount of Al ₂ O ₃ . Al ₂ O ₃ content is within the above range, compared with the case of Al ₂ O ₃ content is outside the above range, a high thermal stability to suppress devitrification during heating, and to suppress crystallization precipitation upon cooling the molten glass. However, from the point of view that Al ₂ O ₃ has little effect on reducing the specific gravity and is a component that has the effect of lowering the refractive index, it is possible to obtain a high refractive index. From the viewpoint of a glass with a low specific gravity, the smaller the content of _{Al 2} O _{3, the better.} In addition, if _{the content of Al 2} O ₃ is too large, the devitrification resistance of the glass will decrease, the glass transition temperature Tg will increase, and the thermal stability may decrease. On the other hand, if _{the content of Al 2} O ₃ is too small, the corrosion of the refractory brick may increase.

Regarding the content and ratio of glass components other than the above in the optical glass of the first embodiment, non-limiting examples are shown below.

In the optical glass of the first embodiment, _{the total content of TiO 2} , CaO, SrO, and Y ₂ O _{3 is} the same as BaO, MgO, Nb ₂ O ₅ , Ta ₂ O ₅ , WO ₃ , Bi ₂ O ₃ , La ₂ O ₃ and the mass ratio of the total content of _{Gd 2} O _{3 [(TiO 2} +CaO+SrO+Y ₂ O ₃ )/(BaO+MgO+Nb ₂ O ₅ +Ta ₂ O ₅ +WO ₃ +Bi ₂ O ₃ + The lower limit of La ₂ O ₃ +Gd ₂ O ₃ )] is preferably 0.5, and more preferably 0.6, 0.7, 0.8, 0.9, 1.0 in order. In addition, the upper limit of the mass ratio is preferably 4.0, and more preferably 3.0, 2.5, 2.0, and 1.5 in this order.

By making the mass ratio [(TiO ₂ +CaO+SrO+Y ₂ O ₃ )/(BaO+MgO+Nb ₂ O ₅ +Ta ₂ O ₅ +WO ₃ +Bi ₂ O ₃ +La ₂ O ₃ +Gd ₂ O ₃ )] In the above range, an optical glass having a high refractive index nd and a low specific gravity can be obtained. If the mass ratio is too small, there is a possibility that high refractive index and low specific gravity cannot coexist. If the mass ratio is too large, the stability of the glass may decrease.

Regarding the optical glass of the first embodiment, the lower limit of the mass ratio [TiO ₂ /Nb ₂ O _{5 ] of the content of TiO 2 and} the content of Nb ₂ O ₅ is preferably 0.5, and further, 0.53, 0.54, 0.55 in this order , 0.6, 0.7, 0.8, 0.9, 1.0 are more preferable. In addition, the upper limit of the mass ratio [TiO ₂ /Nb ₂ O ₅ ] is preferably 4.0, and more preferably 3.0, 2.5, 2.0, and 1.5 in this order.

By setting the mass ratio [TiO ₂ /Nb ₂ O ₅ ] in the above range, the specific gravity of the glass can be reduced while the stability of the glass can be improved. On the other hand, if the mass ratio is too small, the liquidus temperature will rise, the solubility will deteriorate, and the corrosion of the refractory brick when the glass is melted may increase. In addition, there is a risk of increasing manufacturing costs. In addition, if the mass ratio is too large, the devitrification resistance of the glass may be lowered, and the glass transmittance may be lowered.

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

By making the total content [MgO+CaO+SrO+BaO] within the above range, the melting property of the glass can be improved, and the thermal stability of the glass can be improved. On the other hand, if the total content is too small, the meltability of the glass may deteriorate, and the corrosion of the refractory brick when the glass is melted may increase. In addition, if the total content is too large, the desired optical characteristics may not be obtained, and the stability may be reduced.

In the optical glass of the first embodiment, _{the mass ratio of the total content of Li 2} O, Na ₂ O, and K ₂ O to the total content of MgO, CaO, SrO, and BaO [(Li ₂ O+Na ₂ O+ The lower limit of K ₂ O)/(MgO+CaO+SrO+BaO)] is preferably 0.00020, and more preferably 0.001, 0.005, 0.010, 0.050, 0.100 in 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 order.

By setting the mass ratio [(Li ₂ O+Na ₂ O+K ₂ O)/(MgO+CaO+SrO+BaO)] within the above range, the specific gravity of the glass can be easily reduced. In addition, by suppressing the reduction of the glass, it is easy to increase the internal transmittance. On the other hand, if the mass ratio is too small, the glass meltability may deteriorate, and the corrosion of the refractory brick when the glass is melted may increase. In addition, if the mass ratio is too large, the homogeneity of the glass may be reduced due to the volatilization or veining of the glass components, and the stability may also be reduced due to the decrease in viscosity.

In the optical glass of the first embodiment, _{the value obtained by dividing the content of Li 2} O by 29.9, the value obtained by dividing the content of B ₂ O ₃ by 69.6, and the value obtained by dividing the content of _{Li 2 O by 29.9} , The ratio of the total value obtained by dividing the content of _{Na 2 O by 62.0 and the value of dividing the content of K 2 O by 94.2 [(Li 2} O/29.9)/{(B ₂ O ₃ /69.6+ The lower limit of Li ₂ O/29.9+Na ₂ O/62.0+K ₂ O/94.2)}] is preferably 0.10, and more preferably 0.20, 0.30, 0.40, 0.45, 0.50 in order. The upper limit of this ratio is preferably 1.00, and more preferably 0.90, 0.80, 0.70, 0.60, and 0.55 in this order. Here, since the divisor of the content of each glass component is equivalent to the molecular weight of each oxide, the ratio represents the number of Li ions in the glass to the total of Li ions, B ions, Na ions, and K ions The ratio of the number of ions.

By setting the ratio [(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)] in the above range, the filling of the glass can be made more It is dense and does not introduce high-melting, high-refractive-index components such as raising the melting temperature of the glass, and can obtain glass with low specific gravity and high refractive index. Furthermore, as the number of Li ions increases, the heating efficiency when the molten glass is heated by energization is improved, and the fluidity of the molten glass can also be improved. In addition, by making the ratio within the above-mentioned range, while ensuring the solubility of the glass, it is possible to suppress the reductive coloration that may occur when the glass is melted, and there is an effect of increasing the internal transmittance. On the other hand, if the ratio is too small, the specific resistance of the molten glass will increase. Therefore, a higher voltage must be applied during energization and melting. As a result, the corrosion of the refractory brick when the glass is molten may increase. Conversely, if the ratio is too large, the stability of the glass may decrease.

In the optical glass of the first embodiment, _{the lower limit of the content of SiO 2} is 5.0%, and more preferably 8.0%, 11.0%, 13.0%, and 15.0%. In addition _{, the upper limit of the content of SiO 2} is preferably 35.0%, and further preferably 30.0%, 27.0%, 25.0%, 23.0%, and 21.0% in order.

SiO ₂ , a network forming component of glass, has the function of improving the thermal stability, chemical durability, and weather resistance of glass, and increasing the viscosity of molten glass. If _{the content of SiO 2} is too small, the devitrification resistance of the glass tends to decrease. If _{the content of SiO 2} is too large, the refractive index nd may decrease, the viscosity may increase, and the partial dispersion ratios Pg and F may increase.

Regarding the optical glass of the first embodiment, _{the lower limit of the content of ZrO 2} is preferably 0.0000%, and further, in this order, 0.0005%, 0.0010%, 0.0050%, 0.0100%, 0.0500%, 0.1%, 0.5%, 1.0% , 1.5% is better. In addition, _{the upper limit of the content of ZrO 2} is preferably 15.0%, and further preferably 10.0%, 7.0%, 5.0%, 3.0%, and 2.0% in this order.

When melting glass in a melting furnace using refractory bricks, ZrO ₂ from the refractory bricks tends to be introduced into the molten glass. Therefore, when the glass raw material does not contain ZrO ₂ , the glass produced by melting in a melting furnace using refractory bricks may contain a small amount of ZrO ₂ . In addition, there are cases where Zr is supplied to the glass by strengthening the contact of platinum with the molten glass. If _{the content of ZrO 2} is too small, the corrosion of the refractory brick may increase. If _{the content of ZrO 2} is too large, the glass meltability may deteriorate. By setting _{the content of ZrO 2} within the above-mentioned range, it is possible to obtain glass with a high refractive index while suppressing the erosion of bricks. In addition, the meltability and thermal stability of the glass can be maintained.

Regarding the optical glass of the first embodiment, _{the upper limit of the content of P 2} O ₅ is preferably 5.0%, and more preferably 4.0%, 3.0%, 2.0%, 1.0%, and 0.6% in this order. In addition, _{the content of P 2} O ₅ is better, and the lower limit is preferably 0.0%. However, in order to adjust the stability and liquidus temperature of the glass, it can also be introduced in the range of 0.20% or more, or 0.40% or more. The content of P ₂ O ₅ is preferably 0.0%.

By setting _{the content of P 2} O ₅ in the above range, the devitrification of the glass can be suppressed, and the corrosion of the refractory brick when the glass is melted can be suppressed.

Regarding the optical glass of the first embodiment, _{the upper limit of the content of B 2} O ₃ is preferably 15.0%, and further preferably 10.0%, 6.0%, 3.0%, 2.0%, and 1.0% in this order. The lower limit of the content of B ₂ O ₃ is preferably 0.0%, and more preferably 0.1%, 0.2%, 0.4%, and 0.7% in order.

B ₂ O ₃ has the function of improving the thermal stability of the glass and enhancing the melting property of the glass. In addition, among the network forming components of the glass, the refractive index is relatively high and the specific gravity can be reduced. By setting _{the content of B 2} O ₃ within the above-mentioned range, the meltability of the glass can be improved, and an optical glass with a high refractive index and a low specific gravity can be obtained. On the other hand, if _{the content of B 2} O ₃ is too small, the high refractive index may be impaired, and the specific gravity may increase. In addition, if _{the content of B 2} O ₃ is too large, the volatilization amount of the glass component may increase when the glass is melted. In addition, there is a tendency to hinder high dispersion and reduce devitrification resistance.

Regarding the optical glass of the first embodiment, the lower limit of the total content of _{SiO 2} and Al ₂ O _{3 [SiO 2} +Al ₂ O ₃ ] is preferably 5%, and further to 8%, 11%, and 13% in this order. For better. In addition, the upper limit of the total content [SiO ₂ +Al ₂ O ₃ ] is preferably 40%, and more preferably 35%, 30%, 25%, 23%, 21%, 15% in order.

By making the total content [SiO ₂ +Al ₂ O ₃ ] within the above-mentioned range, the corrosion of the refractory bricks when the glass is melted can be suppressed. However, if the total content is too large, the specific gravity will not drop too much, and on the other hand, the refractive index will drop significantly, and the refractive index required by the present invention may not be obtained.

Regarding the optical glass of the first embodiment, the lower limit of the total content of _{B 2} O ₃ and P ₂ O _{5 [B 2} O ₃ +P ₂ O ₅ ] is preferably 0.1%, and further 0.2%, 0.4 in order %, 0.7%, 1% are better. In addition, the upper limit of the total content [B ₂ O ₃ +P ₂ O ₅ ] is preferably 10%, and more preferably 6%, 3%, and 2% in order.

By setting the total content of [B ₂ O ₃ +P ₂ O ₅ ] in the above range, the viscosity of the glass can be maintained and the stability can be improved, and the corrosion of the refractory bricks when the glass is melted can be suppressed.

Regarding the optical glass of the first embodiment, _{the lower limit of the TiO 2} content is preferably 5.0%, and further, 10.0%, 14.0%, 14.2%, 14.5%, 14.8%, 15.0%, 18.0%, and 20.0% in this order For better. In addition _{, the upper limit of the content of TiO 2} is preferably 40.0%, and further preferably 35.0%, 30.0%, 25.0%, and 22.0% in order.

By setting _{the content of TiO 2} in the above range, a glass with a high refractive index and a low specific gravity can be obtained. In addition, it also has the effect of reducing the UV transmittance. On the other hand, if _{the content of TiO 2} is too small, the refractive index may decrease and the specific gravity may increase. In addition, if _{the content of TiO 2} is too large, the visible region of the glass, especially the internal transmittance of the short wavelength region, may be reduced, and the devitrification resistance may also be reduced.

Regarding the optical glass of the first embodiment, _{the lower limit of the Nb 2} O ₅ content is preferably 0.0%, and more preferably 5.0%, 10.0%, 13.0%, and 15.0% in this order. In addition, _{the upper limit of the Nb 2} O ₅ content is preferably 40.0%, and more preferably 35.0%, 30.0%, 28.0%, 27.0%, 26.0%, 25.0%, 20.0%, 17.0% in order.

By setting _{the content of Nb 2} O ₅ in the above range, an optical glass with a high refractive index and a relatively low specific gravity can be obtained. On the other hand, if _{the content of Nb 2} O ₅ is too small, the refractive index may decrease and the specific gravity may increase. If _{the content of Nb 2} O ₅ is too large, the devitrification resistance may decrease.

Regarding the optical glass of the first embodiment, the lower limit of the total content of _{TiO 2} , Nb ₂ O ₅ and ZrO _{2 [TiO 2} +Nb ₂ O ₅ +ZrO ₂ ] is preferably 25%, and further 30% in order , 35%, 40%, 45% are better. In addition, the upper limit of the total content is preferably 75%, and more preferably 70%, 60%, 55%, 52.5%, and 50% in order.

By setting the total content of [TiO ₂ +Nb ₂ O ₅ +ZrO ₂ ] in the above range, it is possible to obtain an optical glass with a high refractive index and high internal transmittance at a predetermined wavelength while suppressing an increase in specific gravity.

Regarding the optical glass of the first embodiment, _{the upper limit of the WO 3} content is preferably 5.0%, and more preferably 3.0%, 2.0%, 1.0%, and 0.5% in this order. The lower limit of the WO ₃ content is preferably 0.0%. The content of WO ₃ may also be 0.0%.

By setting _{the content of WO 3} in the above range, an optical glass with reduced specific gravity and reduced ultraviolet transmittance can be obtained. On the other hand, if _{the content of WO 3} is too large, the partial dispersion ratios Pg and F may increase, the internal transmittance may decrease, and the specific gravity may increase. In addition, the transmittance of the visible region, especially the short-wavelength region, is lowered, and the glass may become unstable.

Regarding the optical glass of the first embodiment, _{the upper limit of the Bi 2} O ₃ content is preferably 5.0%, and more preferably 3.0%, 2.0%, 1.0%, and 0.5% in this order. The lower limit of the content of Bi ₂ O _{3 is preferably 0.0%.} The content of Bi ₂ O ₃ may also be 0.0%.

By setting _{the content of Bi 2} O ₃ within the above range, an optical glass with reduced specific gravity and reduced ultraviolet transmittance can be obtained. On the other hand, if _{the content of Bi 2} O ₃ is too much, the partial dispersion ratio Pg and F will increase, and the specific gravity will increase. Moreover, the Bi ion absorbs light of a specific wavelength, and the transmittance in the short wavelength region also reduces the internal The penetration rate. In addition, there is a risk of increasing the amount of glass erosion of platinum and increasing the coloring of the glass.

Regarding the optical glass of the first embodiment, the total content of _{WO 3} and Bi ₂ O _{3 [WO 3} +Bi ₂ O ₃ ] is preferably 3% or less, and further, 2.4% or less, 1.9% or less, 1.4 % Or less, 0.9% or less, more preferably 0.4% or less. It is particularly preferred that it does not contain WO ₃ and Bi ₂ O _3.

By setting the total content of [WO ₃ +Bi ₂ O ₃ ] within the above-mentioned range, it is possible to suppress the decrease in the internal transmittance in the visible light region in particular.

Regarding the optical glass of the first embodiment, _{the upper limit of the content of Li 2} O is preferably 15.0%, and further preferably 10.0%, 7.0%, 5.0%, 3.0%, and 2.0% in this order. The lower limit of the content of Li ₂ O is preferably 0.0%, and more preferably 0.1%, 0.5%, 1.0%, and 1.5% in order.

By setting _{the content of Li 2} O within the above range, the filling rate of the glass structure can be increased, and an optical glass with a high refractive index and a low 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. Furthermore, it also has the effect of suppressing the reductive coloration that may occur when the glass is melted. On the other hand, if _{the content of Li 2} O is too small, the glass transmittance may decrease. If _{the content of Li 2} O is too large, chemical durability and weather resistance may be reduced, and stability during reheating may be reduced.

Regarding the optical glass of the first embodiment, _{the upper limit of the Na 2} O content is preferably 15.0%, and further preferably 10.0%, 7.0%, 5.0%, 3.0%, and 2.0% in this order. The lower limit of the Na ₂ O content is preferably 0.0%, and more preferably 0.1%, 0.5%, 1.0%, and 1.5% in order.

By making _{the content of Na 2} O within the above-mentioned 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 content of Na 2} O is too small, the glass meltability may decrease. If _{the content of Na 2} O is too large, the refractive index may decrease.

Regarding the optical glass of the first embodiment, _{the upper limit of the K 2} O content is preferably 15.0%, and more preferably 10.0%, 5.0%, 4.0%, 3.0%, 2.0%, and 1.0% in this order. The content of K ₂ O is preferably smaller, and the lower limit is preferably 0.0%, and further preferably 0.1%, 0.3%, 0.6%, and 0.9% in order.

By setting _{the content of K 2} O within the above range, there is an effect of improving the stability of the glass _{containing TiO 2.} In addition, the meltability of the glass can be improved. On the other hand, if _{the content of K 2} O is too large, the refractive index may be significantly lowered.

Regarding the optical glass of the first embodiment, _{the upper limit of the Cs 2} O content is preferably 15.0%, and further preferably 10.0%, 5.0%, 4.0%, 3.0%, 2.0%, and 1.0% in this order. The lower limit of the content of Cs _{2 O is preferably 0.0%.} The content of Cs ₂ O may also be 0.0%.

Cs ₂ O has the effect of enhancing the meltability of the glass and improving the thermal stability. On the other hand _{, if the content of Cs 2} O is too large, the refractive index may be significantly reduced, and the chemical durability of the glass may deteriorate.

Regarding the optical glass of 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 this order. In addition, the content of MgO is better, and the lower limit is preferably 0.0%. The content of MgO may also be 0.0%.

By making the content of MgO in the above range, the stability of the glass can be improved, and the coloring of the glass can be reduced. On the other hand, if the content of MgO is too large, there is a possibility that high refractive index and low specific gravity cannot coexist.

Regarding the optical glass of the first embodiment, the upper limit of the content of CaO is preferably 30.0%, and more preferably 25.0%, 20.0%, 16.0%, and 13.0% in this order. In addition, the lower limit of the content of CaO is preferably 0.0%, and further preferably 3.0%, 6.0%, 8.0%, and 10.0% in order.

By setting the content of CaO in the above range, an optical glass with a high refractive index, a lower specific gravity, and an improved melting property can be obtained. On the other hand, if the content of CaO is too small, there is a possibility that high refractive index and low specific gravity cannot coexist. In addition, if the content of CaO is too large, the erosion amount of the brick will increase, high dispersibility cannot be maintained, the thermal stability of the glass will decrease, and the devitrification resistance may decrease.

Regarding the optical glass of 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 this order. In addition, the content of SrO is better, the lower limit is preferably 0.0%, and the lower limit is 0.1%, 0.5%, 1.0%, and 1.5%, the better.

By making the content of SrO within the above-mentioned range, the meltability can be improved. On the other hand, if the content of SrO is too large, the specific gravity increases, high dispersibility cannot be maintained, the thermal stability of the glass decreases, and the devitrification resistance may decrease.

Regarding the optical glass of the first embodiment, the upper limit of the content of BaO is preferably 30.0%, and more preferably 25.0%, 20.0%, 16.0%, and 13.0% in this order. In addition, the lower limit of the content of BaO is preferably 0.0%, and further preferably 3.0%, 6.0%, 8.0%, and 10.0% in order. The content of BaO may also be 0.0%.

By making the content of BaO within the above-mentioned range, the meltability can be improved. On the other hand, if the content of BaO is too small, the stability of the glass may decrease. In addition, if the content of BaO is too large, the specific gravity may increase significantly, high dispersibility may not be maintained, the thermal stability of the glass may decrease, and the devitrification resistance may decrease.

Regarding the optical glass of 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 this order. In addition, the content of ZnO is better, and the lower limit is preferably 0.0%. The content of ZnO can also be 0.0%.

The content of ZnO in the above range can lower the glass transition temperature Tg. On the other hand, if the content of ZnO is too large, it will increase the specific gravity and may also impair the stability of the glass.

Regarding the optical glass of the first embodiment, _{the upper limit of the La 2} O ₃ content is preferably 10.0%, and more preferably 5.0%, 4.0%, 3.0%, 2.0%, and 1.0% in this order. In addition, the lower limit of the content of _{La 2} O _{3 is preferably 0.0%.}

By setting _{the content of La 2} O ₃ in the above range, the internal transmittance of the glass is not deteriorated, and an optical glass with a high refractive index can be obtained. On the other hand, when _{the content of La 2} O ₃ is small, the refractive index tends to decrease. In addition, if _{the content of La 2} O ₃ is too large, the specific gravity may increase and the thermal stability of the glass may decrease.

Regarding the optical glass of the first embodiment, _{the upper limit of the content of Gd 2} O ₃ is preferably 10.0%, and more preferably 5.0%, 4.0%, 3.0%, 2.0%, and 1.0% in this order. In addition _{, the content of Gd 2} O ₃ is better, and the lower limit is preferably 0.0%.

By setting _{the content of Gd 2} O ₃ in the above range, an optical glass with a high refractive index can be obtained without deteriorating the internal transmittance of the glass. On the other hand, if _{the content of Gd 2} O ₃ is too large, 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 glass.

Regarding the optical glass of the first embodiment, _{the upper limit of the Y 2} O ₃ content is preferably 10.0%, and more preferably 8.0%, 5.0%, 3.0%, 2.0%, and 1.5% in this order. In addition, the lower limit of the content of _{Y 2} O _{3 is preferably 0.0%.}

By introducing Y ₂ O ₃ , for example, instead of ZrO ₂ or Nb ₂ O ₅ in the above range, the internal transmittance of the glass is not deteriorated, and an optical glass with high refractive index and low specific gravity can be obtained. On the other hand, _{the content of Y 2} O ₃ is small, which tends to decrease the refractive index. In addition, if _{the content of Y 2} O ₃ is too large, the thermal stability of the glass may decrease, and the devitrification resistance may decrease.

Regarding the optical glass of the first embodiment, _{the upper limit of the content of GeO 2} is preferably 10.0%, and more preferably 6.0%, 4.0%, 3.0%, 2.0%, and 1.0% in this order. In addition _{, the content of GeO 2} is better, and the lower limit is preferably 0.0%.

GeO ₂ is an expensive glass component, so _{the content of GeO 2} is too large, which may increase the manufacturing cost.

Regarding the optical glass of the first embodiment, _{the upper limit of the content of Ta 2} O ₅ is preferably 5%, and more preferably 3%, 2%, and 1% in this order. In addition, the lower limit of the content of _{Ta 2} O _{5 is preferably 0%.}

Ta ₂ O ₅ is a glass component that does not deteriorate the internal transmittance of the glass to increase the refractive index, and it is also a component that lowers the partial dispersion ratios of Pg and F. On the other hand, Ta ₂ O ₅ is an expensive glass component, and _{the content of Ta 2} O ₅ increases, which may increase the manufacturing cost. In addition, there is a risk of increasing the specific gravity. Therefore, _{the content of Ta 2} O ₅ is preferably within the above range.

In the optical glass of the first embodiment, _{the content of Sc 2} O ₃ is preferably 2% or less. In addition, the lower limit of the content of _{Sc 2} O _{3 is preferably 0%.}

Sc ₂ O ₃ has the effect of increasing the refractive index of the glass, but it is an expensive component. Therefore, _{each content of Sc 2} O ₃ is preferably within the above-mentioned range.

In the optical glass of the first embodiment, _{the upper limit of the content of HfO 2} is preferably 2%, and further is 1.5%, 1.0%, 0.5%, and 0.3%. In addition, _{the lower limit of the content of HfO 2} is preferably 0%, and more preferably 0.005%, 0.01%, 0.03%, 0.05%, 0.07%, and 0.09% in this order.

Furthermore, HfO _{2 may} be contained in a certain amount in the raw material of _{ZrO 2.} Therefore, _{glasses containing ZrO 2} sometimes contain a certain amount of HfO ₂ . Therefore, in the optical glass of the first embodiment, the mass ratio [HfO ₂ /ZrO ₂ ] of the content of _{HfO 2 to the content of ZrO 2} may also become a predetermined range. For example, the lower limit of the mass ratio [HfO ₂ /ZrO ₂ ] can be 0.005, and further can be 0.010, 0.013, or 0.015 in order. On the other hand, the upper limit of the mass ratio can be 0.05, and further can be 0.040, 0.030, 0.020, or 0.018 in order. From the viewpoint of suppressing the melting of the components of the refractory bricks in the glass, it is _{preferable that the glass contains a small amount of ZrO 2} , and for this reason _{, the content of HfO 2} is preferably in the above-mentioned range.

Regarding the optical glass of the first embodiment, _{the content of Lu 2} O ₃ is preferably 2% or less. In addition, the lower limit of the content of _{Lu 2} O _{3 is preferably 0%.}

Lu ₂ O ₃ has the effect of adjusting the refractive index of glass, but from the viewpoint of its high molecular weight, it is a glass component that increases the specific gravity of glass. Therefore, _{the content of Lu 2} O ₃ is preferably within the above-mentioned range.

Regarding the optical glass of the first embodiment, _{the content of Yb 2} O ₃ is preferably 2% or less, more preferably 1% or less, and further preferably 0.5% or less. In addition, the lower limit of the content of _{Yb 2} O _{3 is preferably 0%.}

Yb ₂ O ₃ has the effect of adjusting the refractive index of the glass, but from the point of view of the large molecular weight, it will increase the specific gravity of the glass. As the specific gravity of the glass increases, the quality of the optical element will increase. Therefore, it is better to reduce _{the content of Yb 2} O ₃ to suppress the increase in the specific gravity of the glass.

In addition, if _{the content of Yb 2} O ₃ is too large, the thermal stability of the glass will decrease. Furthermore, it will cause absorption in the infrared region. From the viewpoint of preventing the thermal stability of the glass from decreasing and suppressing the increase in specific gravity, _{the content of Yb 2} O ₃ is preferably within the above-mentioned range.

The optical glass of the first embodiment is mainly composed of the above-mentioned glass components, namely, Al ₂ O ₃ , SiO ₂ , ZrO ₂ , P ₂ O ₅ , B ₂ O ₃ , TiO ₂ , Nb ₂ O ₅ , WO 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 _The composition of 2 O ₅ , Sc ₂ O ₃ , HfO ₂ , Lu ₂ O ₃ and Yb ₂ O _{3 is} preferred. The total content of the above glass components is preferably 95% or more, more preferably 98% or more, and further 99 % Or more is preferable, and 99.5% or more is more preferable.

In addition, the optical glass of the first embodiment is basically preferably composed of the above-mentioned glass components, and other components may be contained within a range that does not hinder the effects of the present invention. In addition, the present invention does not exclude the inclusion of unavoidable impurities.

(Other ingredients) Pb, As, Cd, Tl, Be, and Se are all toxic. Therefore, it is preferable that the optical glass of this embodiment does not contain these elements as a glass component.

U, Th, and Ra are all radioactive elements. Therefore, it is preferable that the optical glass of this embodiment does not contain these elements as a glass component.

V, Cr, Mn, Fe, Co, Ni, Cu, Pr, Nd, Pm, Sm, Eu, Tb, Dy, Ho, Er, Tm will increase the color of glass and may become a source of fluorescence. Therefore, it is preferable that the optical glass of this embodiment does not contain these elements as a glass component. However, elements that do not deteriorate the transmittance near 460 nm, which is the target of the present invention, are introduced in a range that can solve the problem of the present invention.

Sb(Sb ₂ O ₃ ) and Ce(CeO ₂ ) are elements that function as clearing agents and can be added arbitrarily. Among them, Sb (Sb ₂ O ₃ ) is a clearing agent with a great clearing effect. Compared with Sb(Sb ₂ O ₃ ), Ce(CeO ₂ ) has a smaller clearing effect. When Ce(CeO ₂ ) is added in large amounts, there is a tendency to enhance the coloring of the glass.

The content of Sb ₂ O ₃ is expressed as an external percentage. That is, the total content of the all-glass component ₂ other than Sb ₂ O ₃ and CeO as Sb ₂ O ₃ content is 100% by mass, preferably 1.0 mass% or less, and further sequentially to 0.4 mass%, 0.2 mass% Or less, 0.1% by mass or less, 0.05% by mass or less, 0.03% by mass or less, 0.02% by mass or less, and 0.01% by mass or less are more preferable. The content of Sb ₂ O ₃ may also be 0% by mass.

The content of CeO ₂ is also expressed as an external percentage. That is, _{the CeO 2} content when the total content of all glass components other than _{CeO 2} and Sb ₂ O ₃ is taken as 100% by mass is preferably 2% by mass or less, more preferably 1% by mass or less, and further 0.5% by mass The following is preferable, and 0.1 mass% or less is more preferable. The content of CeO ₂ may also be 0% by mass. The clarity of the glass can be improved by setting _{the content of CeO 2 in the above range.}

(Characteristics of glass) <Refractive index nd> In the optical glass of the first embodiment, the upper limit of the refractive index nd may be 2.50, and may further be 2.20, 2.10, 2.05, 2.00, or 1.98. In addition, the lower limit of the refractive index nd may be 1.85, and may be further 1.87, 1.89, or 1.90. The refractive index can be adjusted by adjusting the content of TiO ₂ , Nb ₂ O ₅ , ZrO ₂ , Y ₂ O _3, etc., which can contribute to the high refractive index glass component, or by adjusting SiO ₂ , Al ₂ O ₃ , B ₂ O The content of low-refractive index components such as _{3 , or by introducing modification components such as Li 2} O or CaO can be controlled.

<Abbe number νd> In the optical glass of the first embodiment, the upper limit of the Abbe number νd may be 30.0, and further may be 28.0, 26.0, 25.0, or 24.5 in this order. In addition, the lower limit of the Abbe number νd may be 15.0, and further may be 18.0, 20.0, 22.0, or 23.0 in order. When the Abbe number νd is in the above range, a glass having desired dispersion properties can be obtained. The Abbe number νd can be controlled by adjusting the contents of TiO ₂ , Nb ₂ O ₅ , WO ₃ , ZrO ₂ and Bi ₂ O ₃ that can contribute to the high dispersion of the glass component.

＜Specific gravity of glass＞ Although the optical glass of the first embodiment is a high refractive index glass, the specific gravity is not large. As long as 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 small, the thermal stability will decrease.

Therefore, in the optical glass of 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 this order. The lower limit of the specific gravity is preferably 2.5, and further preferably 3.0 and 3.5 in order.

The specific gravity depends on the atomic weight of the constituent components contained in the glass and the volume occupied by the 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, and when the occupied volume of the element is also large, the increase in specific gravity may sometimes be suppressed. However, if the occupied volume of the element is too large, the refractive index will decrease. In addition, the occupied volume of the element is not inherent, and varies somewhat depending on the presence of other glass components. The specific gravity value can be controlled by adjusting the total measurement and ratio of each component. Furthermore, the occupied volume of each element varies somewhat according to the slow cooling conditions of the glass.

＜Glass transition temperature Tg＞ Regarding an example of the optical glass of the first embodiment, the upper limit of the glass transition temperature Tg is not particularly limited. In consideration of productivity such as the time required for slow cooling, 850°C is preferred, and 800°C, 750°C, 700 ℃, 650℃ is more preferable. In addition, the lower limit of the glass transition temperature Tg is not particularly limited. From the viewpoint of having heat resistance suitable for optical glass, 100°C is preferred, and 200°C, 300°C, 400°C, and 500°C are more preferred in this order.

The glass transition temperature Tg can be controlled by introducing components such as Li or Zn, which are known to reduce Tg, into the glass components, and by adjusting the increase or decrease of glass forming components, the ratio of each component, and the like.

When the upper limit of the glass transition temperature Tg satisfies the above, it is possible to suppress the increase in the molding temperature and the annealing temperature when the glass is reheated and pressed, and it is possible to reduce thermal damage to the reheating press forming equipment and the annealing equipment.

When the lower limit of the glass transition temperature Tg satisfies the above, it is easy to maintain the desired Abbe number and refractive index, while maintaining good reheat press formability and thermal stability of the glass. ＜Liquid temperature LT＞

Regarding the upper limit of the liquidus temperature LT of the optical glass of the first embodiment, from the viewpoint of minimizing the energy used for glass melting, 1450°C is preferred, and 1400°C, 1350°C, 1300°C, 1250°C, 1200°C is more preferable. In addition, the lower limit of the liquidus temperature is not particularly limited. From the viewpoint of obtaining a certain degree of stability, 800°C is preferred, and 900°C, 1000°C, 1050°C, and 1100°C are more preferred in this order. By setting the liquidus temperature in the above range, the corrosion of the refractory bricks when the glass is melted can be suppressed.

In addition, the liquidus temperature is determined as follows. Put 10cc (10ml) of glass into a platinum crucible and melt it at 1250°C to 1450°C for 20-30 minutes, then cool it to below the glass transition temperature Tg, and place the glass with the platinum crucible in a melting furnace at a predetermined temperature for 2 hours. Keep the temperature at 800°C or higher at intervals of 5°C or 10°C. After keeping it for 2 hours, cool it down, and observe whether there are crystals in the glass with a 100 times optical microscope. The lowest temperature at which no crystals precipitate was taken as the liquidus temperature.

＜Pt content＞ Regarding the optical glass of the first embodiment, the upper limit of the Pt content is preferably 10.0 mass ppm, and more preferably 8.0 mass ppm, 7.0 mass ppm, 6.0 mass ppm, and 5.0 mass ppm in this order. The content of Pt is preferably small, and the lower limit is preferably 4.0 mass ppm, and further, 3.0 mass ppm, 2.0 mass ppm, and 0.0 mass ppm are as small as possible.

In a part of the melting furnace, especially the glass produced in the melting furnace where refractory bricks are used for heating and melting the batch of raw materials, the content of Pt can be reduced compared to the glass produced in the platinum furnace. By setting the Pt content in the above range, an optical glass with excellent transmittance can be obtained.

＜τ460, τ440＞ Regarding the optical glass of the first embodiment, the lower limit of the internal transmittance τ460 at a wavelength of 460nm with a thickness of 10.0mm±0.1mm is preferably 88.0%, and further, 90.0%, 91.0%, 92.0%, and 93.0% in this order , 94.0%, 95.0% are better. The higher the internal penetration rate is, the better, 100.0% is better, and the upper limit is 99.0%, 98.0%, 97.0%, and 96.0%, the higher the better. In addition, the thickness (optical path length) of the glass product using the optical glass of the present embodiment can be appropriately selected according to the application, and is not limited to 10.0 mm, and may be, for example, 15 mm or more, further 20 mm or more, or 30 mm or more. It can also be made into 8mm or less, 6mm or less, or 4mm or less according to the application.

In addition, regarding the optical glass of the first embodiment, the lower limit of the internal transmittance τ440 at a wavelength of 440nm with a thickness of 10.0mm±0.1mm is preferably 85.0%, and further sequentially 88.0%, 90.0%, 91.0%, 92.0%, 93.0%, 94.0% are better. The higher the internal penetration rate is, the better, 100.0% is better, and the upper limit is 99.0%, 98.0%, 97.0%, 96.0%, 95.0%, and the higher the better.

在此 τ︰在試料的厚度d₂ 的玻璃的內部穿透率 Δd︰試料的厚度差[d₂ -d₁ ] T1：以試料的厚度d₁ 所得包含表面反射損失的穿透率 T2：以試料的厚度d₂ 所得包含表面反射損失的穿透率The internal transmittance (τ) is the transmittance that removes the surface reflection loss on the incident side and the exit side. Regarding the two glass samples with different thicknesses, the internal transmittance was obtained by the following equation using the measured value of the transmittance including the surface reflection loss at a wavelength of 460 nm or 440 nm, respectively. The thickness d ₁ and d _{2 of the} glass sample are 2.0 mm ± 0.1 mm and 10.0 mm ± 0.1 mm, respectively. [Number 1]

Here τ: _{the internal transmittance of the glass at the thickness d 2} of the sample Δd: the thickness difference of the sample [d ₂ -d ₁ ] T1: the transmittance including the surface reflection loss obtained by the thickness d _{1 of the sample T2:} The transmittance of the thickness d ₂ of the sample including the surface reflection loss

The internal transmittance is the transmittance of the material that does not depend on the refractive index. It can be adjusted by the inherent light absorption of the elements contained in the glass, or the light absorption from impurities such as Pt, and even the glass skeleton. The absorption of the generated coloring center is controlled. From the above point of view, for example, by adjusting _{the content of components such as WO 3} , Bi ₂ O _3, etc., which reduce the internal permeability, the internal permeability can be controlled within the above-mentioned range. In addition, it is also effective to adjust the content of trace components such as _{Sb 2 O 3 and Pt.} Furthermore, it is _{also effective to adjust the content of basic components such as βOH, Li 2} O, Na ₂ O, and K ₂ O to easily reduce reduction and coloration.

＜λτ90, λτ80, λτ5＞ In the optical glass of 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 becomes 90% as shown in Fig. 1. Similarly, λτ80 and λτ5 are wavelengths at which the internal transmittance becomes 80% and 5%, respectively. The internal penetration rate can be obtained by the above formula.

Regarding the optical glass of the first embodiment, the upper limit of λτ90 is preferably 500 nm from the viewpoint of increasing the transmittance at a desired wavelength, and more preferably 470 nm, 450 nm, 430 nm, and 420 nm in this order. The lower limit of λτ90 is not particularly limited. From the viewpoint of reducing the transmittance of short-wavelength light that adversely affects the human body, 150 nm is preferred, and 200 nm, 250 nm, 300 nm, and 350 nm are more preferred.

Regarding the optical glass of 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 this order. There is no particular limitation on the lower limit of λτ80. From the viewpoint of reducing the transmittance of short-wavelength light that adversely affects the human body, 150 nm is preferred, and 200 nm, 250 nm, 300 nm, and 350 nm are further preferred.

Regarding the optical glass of the first embodiment, the upper limit of λτ5 is preferably 390 nm from the viewpoint of increasing the transmittance at a desired wavelength, and more preferably 380 nm, 370 nm, 365 nm, and 360 nm in this order. The lower limit of λτ5 is not particularly limited. From the viewpoint of reducing the transmittance of short-wavelength light that adversely affects the human body, 150 nm is preferred, and 250 nm, 300 nm, 330 nm, 350 nm, and 355 nm are further preferred.

＜λ70＞ Regarding the optical glass of the first embodiment, the upper limit of λ70 is preferably 435nm from the viewpoint of increasing the transmittance at the desired wavelength, and further 430nm, 425nm, 420nm, 415nm, 410nm, 405nm, and 400nm in order Better. There is no particular limitation on the lower limit of λ70. From the viewpoint of achieving coexistence with a high refractive index, 300 nm is preferred, and 310 nm, 320 nm, 330 nm, 340 nm, and 350 nm are more preferred in this order.

The 70% external transmittance of λ70 depends on the internal transmittance and refractive index of the glass, so it is not the best indicator of the properties of the glass of the present invention. However, λ70 having the above-mentioned range as a standard is preferable.

(Manufacturing of optical glass) Regarding the optical glass of the embodiment of the present invention, the glass raw material may be prepared into the above-mentioned predetermined composition, and the prepared glass raw material may be produced in accordance with a conventional glass manufacturing method. For example, a plurality of compounds are blended and mixed thoroughly to make a batch of raw materials, and the batch of raw materials is heated in a crucible made of refractory bricks to make molten glass, which is further cleared and homogenized, then the molten glass is shaped and slowly cooled to obtain optical glass. The clarification or homogenization step can also be melted in an appropriate platinum crucible. When melting in a crucible made of platinum, in order to suppress the oxidation of platinum, it may be melted in a non-oxidizing atmosphere, that is, a nitrogen atmosphere or a water vapor atmosphere. The shaping and slow cooling of molten glass may be performed by a conventional method. In addition, as a raw material for glass, cullet obtained by quenching a molten glass coarsely melted with a refractory brick, a quartz crucible, etc. can be used as a raw material.

In addition, as long as the desired glass component can be introduced into the glass at the desired content, the compound used when preparing batch materials is not particularly limited. However, such compounds include oxides, carbonates, and nitric acid. Salt, hydroxide, water, fluoride, chloride, etc.

In addition, it is also possible to control the amount of hydroxyl groups in the glass as one of means for suppressing the oxidation of glass components due to Pt introduced from a platinum crucible. Regarding the optical glass of this embodiment, since it is a glass mainly composed of silicate, the introduction of excess hydroxyl groups cuts the glass structure, and the thermal stability of the glass may be lowered. This thermal stability affects the degree of crystal precipitation that occurs when the molten glass is slowly cooled, and also affects the crystal precipitation when the glass is reheated. Regarding the optical glass of the present embodiment, in view of the greater influence of the latter, it is better to appropriately control the amount of the hydroxyl group.

The amount of hydroxyl groups in the glass can be expressed by the value of βOH. Regarding the optical glass of the first embodiment, the lower limit of the value of βOH shown in the following formula (1) is ^{preferably 0.1 mm -1} , and further 0.2 mm ^-1 , 0.3 mm ^-1 , and 0.4 mm ^{-1 in this} order Better. In addition, the upper limit of the value of βOH is ^{preferably 1.5mm -1} , and furthermore, 1.2mm ^-1 , 1.0mm ^-1 , 0.9mm ^-1 , 0.8mm ^-1 , 0.7mm ^-1 , 0.6mm ^-1 are more in order. good. βOH=-[ln(B/A)]/t…(1)

Here, in formula (1), t represents the thickness (mm) of the glass used to measure the external transmittance, and A represents that when light is incident on the glass parallel to its thickness direction, it penetrates the outside at a wavelength of 2500nm. Transmittance (%), B represents the external transmittance (%) at a wavelength of 2900 nm when light is incident on the above-mentioned glass parallel to its thickness direction. In addition, ln is the natural logarithm.

Moreover, the so-called "external transmittance" refers to the ratio of the intensity of the light _{penetrating through the glass I out to the intensity of the incident light I in} of the _{incident glass (I out} /I _in ), which also considers the surface reflection of the glass surface The transmittance can be obtained by measuring the transmittance spectrum using a spectrometer.

By evaluating βOH, the content of water (and/or hydroxide ion, hereinafter referred to as "water") in the glass can be evaluated. That is, glass with high βOH means that the water content in the glass is high.

By setting the value of βOH in the above range, devitrification can be suppressed, and an optical glass with high transmittance can be obtained. On the other hand, in the present invention, if the value of βOH is too high, there is a tendency to reduce the thermal stability when the glass is reheated above the glass transition point. In addition, in the slow cooling step of the glass, that is, the maintenance of the high temperature near the strain point and the unit of minutes or hours below the yield point can promote the white turbidity of the glass. The risk of devitrification.

The method of controlling the βOH value is not particularly limited, and examples include using a raw material containing water as a glass raw material, adding water vapor to the melting atmosphere in the melting step, and the like. In addition, when the glass is melted in a melting furnace using refractory bricks, the molten glass is indirectly heated by a gas burner, and at this time, water generated by the combustion of the gas burner is introduced into the molten glass. Thereby, the amount of water in the molten glass can be appropriately increased, so that the value of βOH is within the above range.

(Manufacturing of optical components, etc.) To produce an optical element using the optical glass related to the embodiment of the present invention, a conventional method may be used. For example, in the production of the above-mentioned optical glass, molten glass is poured into a mold to form a plate shape, and a glass material composed of the optical glass of the present invention is produced. The obtained glass material is appropriately cut, ground, and ground to produce slices of a size and shape suitable for press forming. The slice is heated to soften it, and then pressed into a shape (reheated and pressed) by a conventional method to produce an optical element blank with a shape similar to an optical element. The optical element blank is annealed, and the optical element is manufactured by grinding and grinding in a conventional method.

The optical function surface of the manufactured optical element can also be coated with anti-reflection film, total reflection film, etc. according to the purpose of use.

According to an aspect of the present invention, an optical element composed of the above-mentioned optical glass can be provided. Examples of the types of optical elements include flat lenses, spherical lenses, aspheric lenses, and other lenses, triangular prisms, diffraction gratings, and the like. Examples of the shape of the lens include various shapes such as a biconvex lens, a plano-convex lens, a biconcave lens, a plano-concave lens, a convex meniscus lens, and a concave meniscus lens. The optical element can be manufactured by a method including a step of processing a glass molded body composed of the above-mentioned optical glass. Processing can exemplify cutting, cutting, rough grinding, fine grinding, and grinding. When such processing is performed, by using the above-mentioned glass, damage can be reduced, and high-quality optical elements can be stably provided.

Second Embodiment Regarding the optical glass of the second embodiment of the present invention, the total content of _{TiO 2} and Nb ₂ O _{5 [TiO 2} +Nb ₂ O ₅ ] is 20% or more, and _{the content of Al 2} O _{3 is} the same as that of SiO ₂ and The mass ratio of the total content of ZrO _{2 [(Al 2} O ₃ /(SiO ₂ +ZrO ₂ )] is greater than 0.0000.

In the optical glass of the second embodiment, the total content of _{TiO 2} and Nb ₂ O _{5 [TiO 2} +Nb ₂ O ₅ ] 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 order. In addition, the upper limit of the total content is preferably 70%, and more preferably 60%, 57%, 55%, 53%, 50%, 46% in order.

TiO ₂ and Nb ₂ O _{5 are components} that hardly increase specific gravity and contribute to a higher refractive index. Therefore, in order to obtain a glass in which the desired specific gravity and refractive index characteristics coexist, _{the total content of TiO 2} and Nb ₂ O ₅ is preferably within the above-mentioned range.

In the optical glass on the second embodiment, the quality of the content of Al ₂ O ₃ and the total content of SiO ₂ and ZrO ₂ ratio _{[(Al 2 O 3 / (} SiO 2 + ZrO 2)] is greater than 0.0000. The mass ratio of [ The lower limit of (Al ₂ O ₃ /(SiO ₂ +ZrO ₂ )] 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, 0.0450 in this order. The upper limit of the mass ratio is preferably 0.3000, and more preferably 0.2500, 0.2000, 0.1500, 0.1000 in order.

By setting the mass ratio [(Al ₂ O ₃ /(SiO ₂ +ZrO ₂ )] within the above-mentioned range, the corrosion of the refractory bricks during glass melting can be suppressed. In addition, compared with the glass whose ratio is outside the above-mentioned range, there is The effect of improving thermal stability, devitrification during heating, or delaying crystallization when cooling molten glass. On the other hand, if the mass ratio is too large, not only the refractive index nd will be reduced, but also the thermal stability will be reduced. Perplexity.

Hereinafter, a preferable aspect of the optical glass of the second embodiment will be described.

In the optical glass of the second embodiment, the mass ratio of the total content of _{B 2} O ₃ and P ₂ O _{5 to} the total content of SiO ₂ and Al ₂ O _{3 [(B 2} O ₃ +P ₂ O ₅ )/( The upper limit of SiO ₂ +Al ₂ O ₃ )] 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, 0.08 in order. In addition, 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 order.

By setting the mass ratio [(B ₂ O ₃ +P ₂ O ₅ )/(SiO ₂ +Al ₂ O ₃ )] within the above range, it is possible to suppress the corrosion of the glass of the refractory brick during glass melting. If the mass ratio is too large, the corrosion of the refractory bricks will increase, which may reduce the homogeneity of the molten glass and reduce the devitrification resistance.

In the optical glass on the second embodiment, BaO, La ₂ O _3, and the quality of Gd ₂ O ₃ and WO total content of ₃ and the total content of CaO, SrO, and Y ₂ O ₃ ratio of [(BaO + La ₂ The upper limit of O ₃ +Gd ₂ O ₃ +WO ₃ )/(CaO+SrO+Y ₂ O ₃ )] is preferably 3.0, and more preferably 2.7, 2.0, 1.9, 1.8, 1.7, 1.6 in 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 order.

By setting the mass ratio [(BaO+La ₂ O ₃ +Gd ₂ O ₃ +WO ₃ )/(CaO+SrO+Y ₂ O ₃ )] in the above range, components with excessive atomic weight can be restricted or oxygen filling can be promoted. The use of high refractive index components can reduce the specific gravity of the glass. On the other hand, if the mass ratio is too large, the dynamic viscosity of the molten glass will decrease due to the increase in the specific gravity of the glass, making it difficult to control the flow of the glass, etc., which may deteriorate productivity. In addition, there is a risk of increasing the corrosion of refractory bricks.

Regarding the optical glass of the second embodiment, the upper limit of the total content of _{Li 2} O, Na ₂ O, and K _{2 O [Li 2} O+Na ₂ O+K ₂ O] is preferably 13%, and further in order 11%, 10%, 8.0%, 6.0%, 5.0%, 4.0% are more preferable. In addition, the lower limit of the total content is preferably 0.00%, and more preferably 0.01%, 0.1%, 0.5%, 1.0%, 1.5%, 2.0%, and 3.0% in order.

By setting the total content [Li ₂ O+Na ₂ O+K ₂ O] in the above range, the glass viscosity can be appropriately maintained and the productivity of the glass can be improved. In addition, it suppresses the light absorption from the reducing components produced by Ti or Nb, and furthermore, by reducing the melting temperature or slow cooling to promote the elimination of electronic defects in the glass, the internal transmittance of 460nm can be improved. In addition, the corrosion of refractory bricks when the glass is melted can be suppressed. On the other hand, if the total content is too small, the meltability of the glass raw material will deteriorate, and the melting temperature of the raw material must be set high. As a result, the deterioration of the refractory bricks is promoted, and the productivity is deteriorated. Conversely, if the total content is too large, the viscosity of the glass will decrease, and consequently the thermal stability will decrease, which may deteriorate productivity. In addition, the specific resistance of the molten glass decreases, and the heating efficiency when the molten glass is heated by energization is lowered. As a result, the meltability of the glass is lowered, and there is a possibility that productivity may deteriorate. For _{glass with a larger content of Al 2} O ₃ , it is better to avoid excessive adjustment of the aforementioned content.

Regarding the optical glass of the second embodiment, _{the lower limit of the content of Al 2} O ₃ is preferably 0.01%, and further sequentially 0.05%, 0.08%, 0.10%, 0.13%, 0.16%, 0.20%, 0.30%, 0.50%, 0.70%, 1.0% are more preferable. The upper limit of the content of Al ₂ O ₃ is preferably 10.0%, and more preferably 8.0%, 6.0%, 4.0%, and 2.0% in this order.

When melting glass using a refractory brick melting furnace, Al ₂ O ₃ from the refractory brick is introduced into the molten glass. Therefore, even when the glass raw material does not contain Al ₂ O ₃ , the glass produced by melting in a melting furnace using refractory bricks contains a small amount of Al ₂ O ₃ . Al ₂ O ₃ content is within the above range, compared with the case of Al ₂ O ₃ content is outside the above range, a high thermal stability to suppress devitrification during heating, and to suppress crystallization precipitation upon cooling the molten glass. However, from the point of view that Al ₂ O ₃ has little effect on reducing the specific gravity and is a component that has the effect of lowering the refractive index, it is possible to obtain a high refractive index. From the viewpoint of a glass with a low specific gravity, the smaller the content of _{Al 2} O _{3, the better.} In addition, if _{the content of Al 2} O ₃ is too large, the devitrification resistance of the glass will decrease, the glass transition temperature Tg will increase, and the thermal stability may decrease. On the other hand, if _{the content of Al 2} O ₃ is too small, the corrosion of the refractory brick may increase.

Regarding the optical glass of the second embodiment, the contents and ratios of glass components other than the above can be the same as those of the first embodiment. In addition, the glass characteristics, the manufacture of optical glass, the manufacture of optical elements, etc. in the second embodiment may be the same as those in the first embodiment. [Example]

Hereinafter, the present invention will be explained in more detail with examples. However, the present invention is not limited to the aspect shown in the embodiment.

(Example 1) The glass samples of the glass compositions shown in Tables 1 and 2 were prepared in the following steps, and various evaluations were performed.

[Production of Optical Glass] First, prepare oxides, hydroxides, carbonates, and nitrates corresponding to the constituent components of the glass as raw materials. The above-mentioned raw materials are weighed and blended so that the glass composition of the obtained optical glass becomes the composition shown in Tables 1 and 2, which is sufficient. Mix raw materials. The prepared raw materials (batch raw materials) obtained in this way are put into a crucible made of refractory oxides, heated at 1150°C to 1450°C for 1 hour to make molten glass, transferred to a platinum crucible, stirred for homogenization, and cleared, then melted The glass is cast into a metal mold preheated to an appropriate temperature. The cast glass was heat-treated at a temperature 100°C lower than the glass transition temperature Tg for 30 minutes, and cooled to room temperature in a furnace to obtain a glass sample. In addition, in the examples, the amount of raw materials is about 150 g based on oxides.

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

[Measurement of Optical Properties] Regarding the obtained glass sample, after further annealing treatment in the vicinity of the glass transition temperature Tg for about 30 minutes to about 2 hours, it is cooled to room temperature at a temperature drop rate of -30° C./hour in a furnace to obtain an annealed sample. Regarding the obtained annealed sample, the refractive indices nd, ng, nF, and nC, Abbe number νd, τ460, τ440, λτ90, λτ80, λτ5, and λ70 were measured. The results are shown in Table 3. (i) Refractive index nd, ng, nF, nC and Abbe number νd Regarding the aforementioned annealed sample, the refractive index nd, ng, nF, and nC were measured in accordance with the refractive index measurement method of JIS B 7071-1, and the Abbe number νd was calculated based on the following formula. νd=(nd-1)/(nF-nC)

在此 τ︰在試料的厚度d₂ 的玻璃的內部穿透率 Δd︰試料的厚度差[d₂ -d₁ ] T1：以試料的厚度d₁ 所得包含表面反射損失的穿透率 T2：以試料的厚度d₂ 所得包含表面反射損失的穿透率(ii) τ460, τ440 The internal transmittance (τ460, τ440) at wavelengths of 460nm and 440nm is measured. Regarding the two glass samples with different thicknesses, the internal transmittance was obtained by the following equation using the measured value of the transmittance including the surface reflection loss at a wavelength of 460 nm or 440 nm, respectively. The thickness d ₁ and d _{2 of the} glass sample are 2.0 mm ± 0.1 mm and 10.0 mm ± 0.1 mm, respectively. [Number 1]

Here τ: _{the internal transmittance of the glass at the thickness d 2} of the sample Δd: the thickness difference of the sample [d ₂ -d ₁ ] T1: the transmittance including the surface reflection loss obtained by the thickness d _{1 of the sample T2:} The transmittance of the thickness d ₂ of the sample including the surface reflection loss

(iii) λτ90, λτ80, λτ5, λ70 The internal transmittance is measured at a wavelength of 90% (λτ90), the internal transmittance is at a wavelength of 80% (λτ80), the internal transmittance is at a wavelength of 5% (λτ5), and the external transmittance is at a wavelength of 70% ( λ70). The internal penetration rate is calculated by the above formula.

[proportion] The specific gravity is determined by the Archimedes method. The results are shown in Table 3.

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

[Liquid temperature LT] The liquidus temperature LT is determined as follows. Put 10cc (10ml) of glass into a platinum crucible and melt it at 1250°C to 1450°C for 20-30 minutes, then cool it to below the glass transition temperature Tg, and place the glass with the platinum crucible in a melting furnace at a predetermined temperature for 2 hours. Keep the temperature at 800°C or higher at intervals of 5°C or 10°C. After keeping it for 2 hours, cool it down, and observe whether there are crystals in the glass with a 100 times optical microscope. The lowest temperature at which no crystals precipitate was taken as the liquidus temperature. The results are shown in Table 3.

[Pt content] Determine Pt content. The measurement was performed by inductively coupled plasma emission spectroscopy (ICP-AES). The results are shown in Table 3.

[Table 1] Sb ₂ O ₃ 0.02 0.02 0.02 0.02 0.02 0.02 0.02 0.02 0.00 0.02 0.02 0.02 0.02 0.04 0.10 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.02 0.02 0.02 0.02 0.005 0.005 0.02 total 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 WO ₃ 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Bi ₂ O ₃ 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Nb ₂ O ₅ 19.64 19.48 28.91 17.04 19.81 17.09 17.91 19.20 22.52 21.89 22.04 21.93 21.26 20.39 20.39 20.68 20.80 22.61 24.20 23.22 11.69 11.29 11.45 23.52 23.31 21.23 21.08 20.68 20.27 27.26 26.46 21.26 TiO ₂ 17.45 20.16 18.89 17.63 23.97 17.69 27.76 22.58 26.48 25.75 25.92 25.79 23.98 23.98 23.98 23.32 23.45 25.50 27.29 21.76 29.74 28.72 33.34 22.04 21.84 23.94 23.77 23.31 22.86 14.35 14.69 23.98 ZrO ₂ 8.65 8.57 8.05 7.52 3.45 7.52 1.72 1.52 1.79 1.74 1.75 0.00 1.60 1.60 1.60 1.56 1.56 1.71 1.82 7.28 1.64 1.58 1.61 7.37 7.30 1.60 1.59 1.55 1.52 2.33 2.33 1.60 HfO ₂ 0.15 0.14 0.14 0.13 0.06 0.13 0.03 0.03 0.03 0.03 0.03 0.00 0.03 0.03 0.03 0.03 0.03 0.03 0.03 0.12 0.03 0.03 0.03 0.12 0.12 0.03 0.03 0.03 0.03 0.00 0.00 0.03 Y ₂ O ₃ 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 5.90 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Gd ₂ O ₃ 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 La ₂ O ₃ 2.93 2.90 2.72 2.54 2.95 2.55 2.31 2.05 2.40 2.33 0.00 2.34 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 2.21 2.13 2.16 0.00 0.00 0.00 0.00 0.00 0.00 11.73 11.76 0.00 ZnO 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 BaO 0.00 0.00 0.00 19.12 0.00 19.18 13.05 19.26 9.04 12.08 14.37 14.30 17.74 18.76 18.75 17.25 17.35 18.86 20.19 18.54 20.76 20.04 20.32 18.78 20.47 17.71 17.59 17.25 16.91 3.34 3.35 17.74 SrO 0.00 0.00 0.00 0.00 0.00 0.00 0.00 3.91 0.00 0.00 0.00 0.00 2.40 2.40 2.40 2.33 2.35 2.55 2.73 3.13 0.00 0.00 0.00 0.00 0.00 2.39 2.38 2.33 2.29 1.68 1.68 2.40 CaO 25.89 21.68 18.07 11.97 22.05 12.01 9.15 8.10 9.50 7.63 8.49 8.45 8.53 8.53 8.53 8.29 8.34 9.07 9.71 9.91 8.73 8.43 8.55 11.68 10.89 8.51 8.46 8.29 8.13 14.68 14.71 8.53 MgO 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 1.32 3.00 2.90 2.94 0.00 0.00 0.00 0.00 0.00 4.76 0.00 0.00 0.00 Cs2O 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 K ₂ O 0.00 0.00 0.00 0.00 0.00 0.00 3.67 0.59 0.69 2.02 0.68 0.68 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Na ₂ O 0.00 0.00 0.00 0.00 0.00 0.00 0.00 1.75 2.05 2.00 2.01 2.00 2.25 2.25 2.25 2.19 2.21 2.40 2.57 0.00 0.00 0.00 0.00 0.00 0.00 2.25 2.24 2.19 2.15 0.00 0.00 2.25 Li ₂ O 1.46 1.45 1.36 1.27 1.48 1.28 2.54 1.50 3.08 2.68 2.69 2.68 1.68 1.68 1.68 1.63 1.64 1.79 1.91 1.78 1.62 1.56 1.58 1.80 1.78 1.68 1.67 1.63 1.60 1.65 1.75 1.68 B ₂ O ₃ 2.35 2.33 2.18 2.04 2.37 2.04 1.98 1.75 2.05 2.00 2.01 2.00 0.92 0.92 0.92 0.90 0.90 0.98 1.05 0.84 1.89 0.91 0.92 1.07 1.48 0.92 0.91 0.90 0.88 2.87 3.00 0.92 GeO ₂ 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 2.69 5.41 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Al ₂ O ₃ 0.20 0.01 0.30 0.40 0.20 0.10 0.30 0.40 0.03 0.06 0.08 0.01 0.10 0.01 0.01 0.20 0.02 0.20 0.03 0.19 0.10 0.01 0.20 0.01 0.06 0.30 1.00 2.91 0.04 0.28 0.12 0.00 SiO ₂ 21.31 23.28 19.41 20.36 23.68 20.43 19.60 17.36 20.33 19.80 19.93 19.83 19.51 19.47 19.47 18.93 15.93 14.32 8.48 11.94 18.61 16.49 16.92 13.62 12.76 19.43 19.30 18.93 18.56 19.85 20.15 19.61 No. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 twenty one twenty two twenty three twenty four 25 26 27 28 29 30 31 Comparative example A

[Table 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) 0.59 0.59 0.59 0.59 0.59 0.59 0.56 0.46 0.60 0.52 0.57 0.57 0.53 0.53 0.53 0.53 0.53 0.53 0.53 0.83 0.67 0.80 0.80 0.80 0.74 0.53 0.53 0.53 0.53 0.57 0.58 0.53 (Li ₂ O+Na ₂ O+K ₂ O)/ (MgO+CaO+SrO+BaO) 0.06 0.07 0.08 0.04 0.07 0.04 0.28 0.12 0.31 0.34 0.24 0.24 0.14 0.13 0.13 0.14 0.14 0.14 0.14 0.05 0.05 0.05 0.05 0.06 0.06 0.14 0.14 0.14 0.12 0.08 0.09 0.14 (MgO+CaO+ SrO+BaO) 25.89 21.68 18.07 31.09 22.05 31.19 22.20 31.27 18.54 19.71 22.86 22.75 28.67 29.69 29.68 27.87 28.04 30.48 32.63 32.90 32.49 31.37 31.81 30.46 31.36 28.61 28.43 27.87 32.09 19.69 19.74 28.67 TiO ₂ /Nb ₂ O ₅ 0.89 1.03 0.65 1.03 1.21 1.04 1.55 1.18 1.18 1.18 1.18 1.18 1.13 1.18 1.18 1.13 1.13 1.13 1.13 0.94 2.54 2.54 2.91 0.94 0.94 1.13 1.13 1.13 1.13 0.53 0.56 1.13 (TiO ₂ +CaO+SrO+Y ₂ O ₃ )/(BaO+MgO+Nb ₂ O ₅ +Ta ₂ O ₅ +WO ₃ +Bi ₂ O ₃ +La ₂ O ₃ +Gd ₂ O ₃ ) 1.92 1.87 1.17 0.76 2.02 0.77 1.11 0.85 1.06 0.92 0.95 0.89 0.90 0.89 0.89 0.89 0.89 0.90 0.90 0.81 1.02 1.18 1.14 0.80 0.75 0.89 0.90 0.89 0.79 0.73 0.75 0.90 (B ₂ O ₃ +ZnO+La ₂ O ₃ +Gd ₂ O ₃ +WO ₃ ) /(SiO ₂ +CaO+TiO ₂ +Nb ₂ O ₅ ) 0.06 0.06 0.06 0.07 0.06 0.07 0.06 0.06 0.06 0.06 0.03 0.06 0.01 0.01 0.01 0.01 0.01 0.01 0.02 0.01 0.06 0.05 0.04 0.02 0.02 0.01 0.01 0.01 0.01 0.19 0.19 0.01 (TiO ₂ +Nb ₂ O ₅ +ZrO ₂ )/ (B ₂ O ₃ +SiO ₂ +Al ₂ O ₃ ＋GeO ₂ ) 1.92 1.88 2.55 1.85 1.80 1.87 2.17 2.22 2.27 2.26 2.26 2.18 2.28 2.25 2.25 2.01 2.06 3.21 5.58 4.03 2.09 2.39 2.57 3.60 3.67 2.26 2.19 2.00 2.29 1.91 1.87 2.28 Al ₂ O ₃ /(SiO ₂ +ZrO ₂ ) 0.0067 0.0003 0.011 0.014 0.0074 0.0036 0.014 0.021 0.0014 0.0028 0.0037 0.0005 0.0047 0.0005 0.0005 0.010 0.0011 0.012 0.0029 0.010 0.0049 0.0006 0.011 0.0005 0.0030 0.014 0.048 0.14 0.0020 0.01 0.0053 0.0000 (BaO+La ₂ O3+Gd ₂ O ₃ +WO ₃ ) /(CaO+SrO+Y ₂ O ₃ ) 0.11 0.13 0.15 1.81 0.13 1.81 1.68 1.77 1.20 1.89 1.69 1.97 1.62 1.72 1.72 1.62 1.62 1.62 1.62 1.42 2.63 1.55 2.63 1.61 1.88 1.62 1.62 1.62 1.62 0.92 0.92 1.62 (B ₂ O ₃ +P ₂ O ₅ )/ (SiO ₂ +Al ₂ O ₃ ) 0.11 0.10 0.11 0.10 0.10 0.10 0.10 0.10 0.10 0.10 0.10 0.10 0.05 0.05 0.05 0.05 0.06 0.07 0.12 0.07 0.10 0.06 0.05 0.08 0.12 0.05 0.04 0.04 0.05 0.14 0.15 0.05 Li ₂ O+Na ₂ O+K ₂ O 1.46 1.45 1.36 1.27 1.48 1.28 6.21 3.84 5.82 6.70 5.38 5.36 3.93 3.93 3.93 3.82 3.85 4.19 4.48 1.78 1.62 1.56 1.58 1.80 1.78 3.93 3.91 3.82 3.75 1.65 1.75 3.93 No. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 twenty one twenty two twenty three twenty four 25 26 27 28 29 30 31 A

[table 3] No. proportion nd vd Glass transition temperature Tg (℃) Liquidus temperature LT (℃) Pt content (mass ppm) λτ90 (nm) λτ80 (nm) λτ5 (nm) τ460 (%) τ440 (%) βOH (mm ^-1 ) λ70 (nm) 1 3.59 1.87939 28.31 696.9 1300 3.9 435 405 365 93.4 90.9 416 2 3.58 1.88972 26.84 672.2 1260 4.8 445 406 365 92.5 89.0 425 3 3.71 1.93950 24.48 1400 5.2 438 407 366 93.0 90.3 425 4 3.90 1.89198 27.09 673.5 1260 4.8 438 413 366 94.0 90.2 427 5 3.52 1.89786 25.67 661.3 1260 5.8 438 411 365 93.8 90.3 424 6 3.90 1.88879 27.28 669.6 1190 2.1 416 398 365 95.6 94.1 0.38 401 7 3.91 1.91305 23.64 615.6 1235 4.6 431 407 366 94.6 91.9 418 8 3.91 1.91307 24.90 615.6 1230 4.4 430 407 366 94.8 92.2 415 9 3.64 1.92548 23.24 589.5 1140 3.7 433 408 366 94.4 91.5 0.54 421 10 3.68 1.91707 23.36 588.5 1130 3.7 428 405 366 95.3 92.7 0.49 415 11 3.70 1.92808 23.40 592.4 1145 4.4 437 411 366 94.0 90.7 0.55 425 12 3.72 1.92222 23.42 597.0 1130 2.1 425 403 366 95.4 93.1 0.42 410 13 3.83 1.92043 23.99 628.9 1165 2.1 423 402 366 95.5 93.5 0.47 409 14 3.84 1.91655 24.18 619.1 1165 4.4 431 409 366 94.8 92.1 0.63 418 15 3.84 1.91671 24.20 620.2 1165 4.4 434 414 367 94.9 91.6 0.67 424 16 3.84 1.91551 24.16 1170 3.0 424 402 366 95.4 93.2 0.51 410 17 3.91 1.92860 23.85 625.4 1170 3.7 424 403 366 95.9 93.6 0.61 410 18 3.78 1.90296 24.97 1200 1.4 406 395 365 98.0 97.1 0.5 397 19 3.83 1.91842 24.04 1230 3.4 414 399 366 97.1 95.5 403 20 4.12 1.97733 23.91 651.4 1260 3.5 427 405 365 96.1 93.1 422 twenty one 3.84 1.93099 23.95 643.8 1180 4.2 434 408 366 95.0 91.6 0.47 422 twenty two 3.97 1.94583 24.40 665.8 1130 4.5 431 407 366 95.1 92.1 0.43 421 twenty three 3.90 1.96698 22.63 657.7 1180 2.7 431 403 365 94.7 92.2 0.44 412 twenty four 4.05 1.97588 23.63 654.7 1260 5.2 434 411 366 95.0 91.5 429 25 4.09 1.97725 23.63 649.7 1260 5.2 430 407 365 95.7 92.6 423 26 3.82 1.91860 24.05 629.7 1170 4.5 433 407 366 94.6 91.6 0.45 420 27 3.81 1.91433 24.03 629.5 1190 4.0 432 406 366 94.8 91.8 0.46 418 28 3.77 1.90213 24.02 629.2 1210 5.0 437 405 365 92.9 90.4 0.43 420 29 3.80 1.90143 25.27 623.4 1220 4.2 427 404 365 94.7 92.5 0.37 412 30 3.84 1.9036 27.0 653 1210 2 417 395 356 96.1 94.3 0.5 407 31 3.83 1.9008 27.1 640 1200 2 410 391 362 96.3 95.1 0.5 400 Comparative example A 3.832 1.92274 23.88 629.7 1165 11 471 434 370 87.9 82.2 449

(Example 2) [Corrosion test of refractory bricks] The glass samples of No. 13, 26, 27, 28 and the glass composition of Comparative Example A in Table 1 were produced in the same procedure as in Example 1, and the evaluation of the corrosion of the refractory bricks was performed in the following procedure.

A 40cc glass sample was melted by heating it in a platinum crucible at 1280°C for 30 minutes. A cylindrical brick sample (ZB-1711VF made by AGC ceramics, SiO ₂ :ZrO ₂ :Al ₂ O ₃ ratio of about 1:4:5, diameter 20mm, length 100mm) was immersed in a glass sample melted in a platinum crucible , Heated at 1280°C for 72 hours. After heating, take out the brick sample.

The taken out brick sample was longitudinally cut into half through the center of the sample. In the cross section, the width of the sample corresponds to the diameter. The photograph of the cross section is shown in Fig. 1. As shown in Fig. 1, in the comparative example, the liquid surface portion of the molten glass sample was damaged such as necking during immersion. In addition, the part immersed in the molten glass sample was corroded as a whole to reduce the diameter. On the other hand, in the examples, the brick samples did not have obvious damage such as necking, and the partial erosion of the glass samples immersed in the molten glass was also small.

The taken-out brick samples were evaluated as follows. First, in the cross section, as shown in Fig. 2, the diameter before the corrosion test and the minimum value of the diameter (diameter of the necked position) occurring near the contact part of the glass surface after the corrosion test are measured. Diameter below 25mm. Based on the following formula, the diameter increase/decrease rate (%) and the average increase/decrease rate ΔD after the erosion test were evaluated. In addition, the diameter does not include the glass or glass deterioration part adhering to the surface of the brick sample.

Increase/decrease rate D _N (%)=([Minimum value of diameter (diameter of necking position)]-[Diameter before erosion test])/[Diameter before erosion test]×100

Increase/decrease rate D ₂₅ (%)=([Diameter under 25mm of the necking position after erosion test]-[Diameter before erosion test])/[Diameter before erosion test]×100

Average increase/decrease rate ΔD=(Increase/decrease rate D _N + Increase/decrease rate D ₂₅ )/2

In the above formula, the diameter of the brick sample is measured 3 times with a digital vernier caliper that can display to 0.01mm, and the average value (unit: mm) is rounded to the first decimal place. . Based on the absolute value (|ΔD|) of the average increase/decrease rate ΔD, the degree of erosion is judged by the classification as shown in Table 4. The results are shown in Table 5.

[Table 4] According to the judgment of |ΔD| judgement result mark Within 4% Less erosion of bricks I Within 10% Brick erosion is slightly less II Within 30% Brick erosion is slightly more III More than 30% Brick erosion is much IV

[table 5] According to the judgment of |ΔD| III II II I I Average increase and decrease rate ΔD -17.9% -5.2% -4.7% -3.47% +2.21% The rate of increase/decrease below 25mm of the necking position D ₂₅ -18.1% -2.5% -2.9% -1.0% +2.5% Increase and decrease rate of necking position D _N -17.6% -7.9% -6.4% -5.9% +2.0% Diameter of brick sample (mm) After erosion test Diameter 25mm below the necking position 16.7 19.8 19.8 20.0 20.9 Diameter of necking position 16.8 18.7 19.1 19.0 20.8 Before erosion test 20.4 20.3 20.4 20.2 20.4 No. Comparative example A 13 26 27 28

(Example 3) Using each optical glass produced in Example 1, a lens blank was produced by a conventional method, and the lens blank was processed by a conventional method such as grinding to produce various lenses. The optical lenses produced are various lenses such as flat lenses, double-convex lenses, double-sided concave lenses, plano-convex lenses, plano-concave lenses, concave meniscus lenses, and convex meniscus lenses. Here, a member obtained by cutting the optical glass without being softened by heating may be used as a lens blank. Various lenses, by matching with lenses composed of other kinds of optical glass, can well correct the secondary chromatic aberration.

In addition, since the glass has a low specific gravity, each lens has a smaller weight than a lens with the same optical characteristics and size, and is suitable for use in goggles or glasses-type AR display devices. Similarly, various optical glasses produced in Example 1 were used to produce triangular prisms.

The embodiment disclosed this time is merely an illustration in all points and should be regarded as not limiting. The scope of the present invention is shown not by the above description but by the scope of the patent application, and it is intended to include all changes within the meaning and scope equivalent to the scope of the patent application.

For example, by performing the composition adjustment described in the specification on the glass composition exemplified above, it is possible to produce an optical glass according to an aspect of the present invention. In addition, it is of course possible to combine two or more items illustrated in the specification or described as a preferable range.

without.

[FIG. 1] is an example of the optical glass of this embodiment, a graph showing the internal transmittance, and shows the wavelength λτ90 at which the internal transmittance is 90%. [Figure 2] is a photograph showing the results of the erosion test of the brick sample in Example 2. [Fig. 3] is a diagram showing the position where the diameter of the brick sample was measured in the erosion test of Example 2.

Claims (6)

An optical glass, the mass ratio of the total content of _{BaO, La 2} O ₃ , Gd ₂ O ₃ and WO _{3 to} the total content of CaO, SrO and Y ₂ O _{3 [(BaO+La 2} O ₃ +Gd ₂ O ₃ +WO ₃ )/(CaO+SrO+Y ₂ O ₃ )] is 2.0 or less, the mass ratio of the total content of _{B 2} O ₃ and P ₂ O _{5 to} the total content of SiO ₂ and Al ₂ O _{3 [(B 2} O ₃ +P ₂ O ₅ )/(SiO ₂ +Al ₂ O ₃ )] is 0.10 or less, the total content of _{Li 2} O, Na ₂ O, and K _{2 O [Li 2} O+Na ₂ O+K ₂ O] 10 mass% or less, Al ₂ O ₃ mass content and the total content of SiO ₂ and ZrO ₂ ratio _{[(Al 2 O 3 / (} SiO 2 + ZrO 2)] is greater than 0.0000. An optical glass in which the total content of _{TiO 2} and Nb ₂ O _{5 [TiO 2} +Nb ₂ O ₅ ] is 20% by mass or more, and the mass ratio of the content of _{Al 2} O ₃ to _{the total content of SiO 2} and ZrO _{2 [(} Al ₂ O ₃ /(SiO ₂ +ZrO ₂ )] is greater than 0.0000. Such as the optical glass of claim 2, wherein the mass ratio of the total content of _{B 2} O ₃ and P ₂ O _{5 to} the total content of SiO ₂ and Al ₂ O _{3 [(B 2} O ₃ +P ₂ O ₅ )/(SiO ₂ +Al ₂ O ₃ )] is 0.15 or less. For the optical glass of claim 2 or 3, the mass ratio of the total content of _{TiO 2} , Nb ₂ O ₅ and ZrO _{2 to} the total content of B ₂ O ₃ , SiO ₂ , Al ₂ O ₃ and GeO _{2 [(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, the total content of _{BaO, La 2} O ₃ , Gd ₂ O ₃ and WO _{3 is equal to} The mass ratio of the total content of CaO, SrO, and Y ₂ O _{3 [(BaO+La 2} O ₃ +Gd ₂ O ₃ +WO ₃ )/(CaO+SrO+Y ₂ O ₃ ) is 3.0 or less. For the optical glass of any one of claims 2 to 4, the mass ratio of the total content of _{TiO 2} , Nb ₂ O ₅ and ZrO _{2 to} the total content of B ₂ O ₃ , SiO ₂ , Al ₂ O ₃ and GeO ₂ [(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, B ₂ O ₃ , ZnO, La ₂ O ₃ , Gd ₂ The mass ratio of the total content of O ₃ and WO _{3 to} the total content of SiO ₂ , CaO, TiO ₂ and Nb ₂ O _{5 [(B 2} O ₃ +ZnO+La ₂ O ₃ +Gd ₂ O ₃ +WO ₃ )/ (SiO ₂ +CaO+TiO ₂ +Nb ₂ O ₅ )] is 0.15 or less. An optical element composed of the optical glass of any one of claims 1 to 5.

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