TW202319362A - Optical glass and optical element having high refractive index, high dispersion characteristic, small specific gravity and good homogeneity - Google Patents

Abstract

The present invention relates to optical glass with high refractive index, high dispersion characteristic, small specific gravity and good homogeneity, and an optical element made therefrom. The optical glass, expressed in mass%, has a SiO2 content of 20-51%, a TiO2 content of 20-40%, a Na2O content of 5-28%, a BaO content of less than 2.0%, a total content (R2O) of Li2O, Na2O, K2O and Cs2O of 8-28%, a ratio [SiO2/(SiO2+B2O3+P2O5)] of SiO2 content to the total content of SiO2, B2O3 and P2O5 (SiO2+B2O3+P2O5) of 0.90 or above, a mass ratio [SiO2/R2O] of SiO2 to R2O of 1.5-3.2, a mass ratio [(SiO2+R2O)/(TiO2+Nb2O5)] of SiO2 and R2O (SiO2+R2O) to TiO2 and Nb2O5 (TiO2+Nb2O5) of 2.6 or less, a mass ratio [TiO2/(TiO2+Nb2O5+ZrO2)] of TiO2 to TiO2, Nb2O5 and ZrO2 (TiO2+Nb2O5+ZrO2) of 0.90 or above, a mass ratio [(CaO+BaO)/R'O] of CaO and BaO(CaO+BaO) to MgO, CaO, SrO and BaO (R'O) of 0.90 or above, a mass ratio [(Na2O+K2O)/R2O] of Na2O and K2O to R2O of 0.98 or above, a mass ratio [BaO/(Na2O+K2O+CaO)] of BaO to Na2O, K2O and CaO of 0.15 or less, and a mass ratio [BaO/(TiO2+Nb2O5)] of BaO to TiO2 and Nb2O5 of 0.12 or less.

Description

Optical Glass and Optical Components

The present invention relates to optical glasses and optical components.

Optical glass with high refractive index and high dispersion characteristics (low Abbe number) is in great demand as a material for optical elements such as various lenses. For example, by combining it with a high-refractive-index low-dispersion lens, a compact and highly functional optical system for chromatic aberration correction can be configured. Furthermore, by aspherizing the optically functional surface of a lens having a high refractive index and high dispersion characteristic, it is possible to achieve further high functionality and miniaturization of various optical systems.

There is known a high refractive index high dispersion optical glass in which components such as Nb ₂ O ₅ and TiO ₂ that impart high refractive index and high dispersion characteristics are added to SiO ₂ , which is a network forming component of glass. Such high-refractive-index high-dispersion optical glasses are described in Patent Documents 1 to 3. Prior Art Documents Patent Documents

Patent Document 1: Japanese Patent Laid-Open No. 2005-097036; Patent Document 2: Japanese Patent Application Publication No. 2016-521237; Patent Document 3: Japanese Patent Laid-Open No. 2018-168011.

The problem to be solved by the invention

In the SiO ₂ -Nb ₂ O ₅ -TiO ₂ system such as the optical glass disclosed in Patent Documents 1 and 2, when the content of the alkali metal component is large, when the glass is melted, the bricks (refractory materials) constituting the melting tank have will be corroded by molten glass. As a result, foreign matter from the refractory material will be mixed into the glass, which will contaminate the glass. In addition, there is a problem that the life of the melting tank is shortened.

Foreign matter in the glass becomes a source of light scattering, reducing the quality of optical glass. In addition, when the glass is heated, softened, and shaped, foreign matter becomes a starting point for crystallization, and the glass tends to devitrify.

In addition, the SiO ₂ -Nb ₂ O ₅ -TiO ₂ -based high-refractive-index high-dispersion glass has a problem of high specificity because it contains a large amount of Nb ₂ O ₅ . In the optical glass disclosed in Patent Document 3, although the content of Nb ₂ O ₅ was reduced, since the content of BaO was large, the specific gravity could not be sufficiently reduced.

The purpose of the present invention is to solve the above problems, and provide an optical glass with high refractive index and high dispersion, low specific gravity, and good homogeneity, and an optical element made of the optical glass. solutions to problems

(1) An optical glass, represented by mass %, the content of SiO ₂ is 20-51%, the content of TiO ₂ is 20-40%, the content of Na ₂ O is 5-28%, and the content of BaO is less than 2.0%, The total content of Li ₂ O, Na ₂ O, K ₂ O and Cs ₂ O (R ₂ O) is 8~28%, the content of SiO ₂ and the total content of SiO ₂ , B ₂ O ₃ and P ₂ O ₅ ( SiO ₂ +B ₂ O ₃ +P ₂ O ₅ ) mass ratio [SiO ₂ /(SiO ₂ +B ₂ O ₃ +P ₂ O ₅ )] is 0.90 or more, SiO ₂ content to R ₂ O mass ratio [SiO ₂ /R ₂ O] is 1.5~3.2, the total content of SiO ₂ and R ₂ O (SiO ₂ +R ₂ O) and the total content of TiO ₂ and Nb ₂ O ₅ (TiO ₂ +Nb ₂ O ₅ ) mass ratio [(SiO ₂ +R ₂ O)/(TiO ₂ +Nb ₂ O ₅ )] is 2.6 or less, the content of TiO ₂ and the total content of TiO ₂ , Nb ₂ O ₅ and ZrO ₂ (TiO ₂ + The mass ratio of Nb ₂ O ₅ +ZrO ₂ ) [TiO ₂ /(TiO ₂ +Nb ₂ O ₅ +ZrO ₂ )] is 0.90 or more, and the total content of CaO and BaO (CaO+BaO) is comparable to that of MgO, CaO, SrO and The mass ratio [(CaO+BaO)/R'O] of the total content of BaO (R'O) is 0.90 or more, and the mass ratio of the total content of Na ₂ O and K 2 O to _{R 2 O} [(Na ₂ O+ K ₂ O)/R ₂ O] is 0.98 or more, and the mass ratio of the BaO content to the total content of Na ₂ O, K ₂ O, and CaO [BaO/(Na ₂ O+K ₂ O+CaO)] is 0.15 or less , the mass ratio [BaO/(TiO ₂ +Nb ₂ O ₅ )] of the content of BaO to the total content of TiO ₂ and Nb ₂ O ₅ is 0.12 or less.

(2) The optical glass according to (1), wherein the refractive index nd is 1.67 to 1.77, and the Abbe number νd is 26 to 33.

(3) The optical glass as described in (1) or (2) whose specific gravity is 3.40 or less.

(4) An optical element comprising the optical glass described in any one of (1) to (3). Invention effect

According to one aspect of the present invention, it is possible to provide an optical glass having a high refractive index and high dispersion characteristics, a small specific gravity, and good homogeneity. Moreover, according to one aspect of this invention, the optical element comprised from the said optical glass can be provided.

In the present invention and this specification, unless otherwise specified, the glass composition of optical glass is expressed on an oxide basis. Here, the "glass composition based on oxides" refers to a glass composition in which glass raw materials are completely decomposed during melting and converted into substances that exist as oxides in optical glass, and the notation of each glass component is described as SiO ₂ , TiO ₂ , etc. Unless otherwise specified, the content and total content of glass components are based on mass, and "%" means "mass %".

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

One embodiment of the present invention will be described below.

The optical glass of the present embodiment contains SiO ₂ , TiO ₂ , and Na ₂ O as essential components.

In the optical glass of the present embodiment, the content of SiO ₂ is 20 to 51%. The lower limit of the content of SiO ₂ is preferably 25%, more preferably 30%, further preferably 33%. From the viewpoint of maintaining the refractive index, the upper limit of the content of SiO ₂ is preferably 50%, more preferably 49%, and still more preferably 48%.

SiO ₂ is a glass network forming component. When the content of SiO ₂ is less than 20%, the thermal stability of the glass decreases and the liquidus temperature rises. In addition, the viscosity of the glass at the time of melting decreases, and bricks (refractory materials) constituting the melting tank and the like are easily corroded. When the content of SiO ₂ is more than 51%, the refractive index nd decreases, making it difficult to manufacture glass having desired optical characteristics. By making the content of SiO ₂ within the above-mentioned range, thermal stability can be maintained, and corrosion of refractory materials can be suppressed.

In the optical glass of the present embodiment, the content of TiO ₂ is 20 to 40%. TiO ₂ is a component that imparts high refractive index and high dispersion characteristics. Nb ₂ O ₅ and ZrO ₂ similarly impart high refractive index and high dispersion characteristics, but TiO ₂ is less likely to increase the specific gravity of glass than Nb ₂ O ₅ and ZrO ₂ . When the TiO ₂ content is more than 40%, the dispersion is too high, the thermal stability of the glass is reduced, and the coloring of the glass is enhanced. On the other hand, when the content of TiO ₂ is less than 20%, it is difficult to obtain a desired refractive index.

Therefore, from the viewpoint of obtaining a desired refractive index, the lower limit of the content of TiO ₂ is preferably 22%, more preferably 24%, and still more preferably 25%. From the viewpoint of maintaining thermal stability, suppressing coloration, and realizing desired dispersion, the upper limit of the TiO ₂ content is preferably 38%, more preferably 36%, and still more preferably 35%. By making the content of TiO ₂ within the above-mentioned range, it is possible to suppress an increase in specific gravity, maintain the thermal stability of the glass, and realize desired optical characteristics.

In the optical glass of the present embodiment, the content of Na ₂ O is 5 to 28%. Na ₂ O has the function of improving the meltability of glass and adjusting the viscosity of molten glass. When the content of Na ₂ O is less than 5%, the function of adjusting the viscosity becomes insufficient. On the other hand, when the content of Na ₂ O is more than 28%, the refractive index decreases, the viscosity of the molten glass decreases and the erosion of the refractory material by the molten glass becomes significant.

Therefore, from the viewpoint of improving the meltability and making the viscosity of the molten glass appropriate, the lower limit of the content of Na ₂ O is preferably 8%, and more preferably 10%, 12%, and 13% in this order. On the other hand, from the viewpoint of suppressing corrosion of the refractory material during glass melting and realizing a desired refractive index, the upper limit of the Na ₂ O content is preferably 25%, and more preferably 23%, 21%, and 19% in this order. %, 17%.

In the optical glass of the present embodiment, the content of BaO is less than 2.0%. BaO is a component that increases the specific gravity. Therefore, the upper limit of the content of BaO is preferably 1.5%, more preferably 1.0%, and further preferably 0.5%. The lower limit of the content of BaO is preferably 0%. The content of BaO may also be 0%. An increase in specific gravity can be suppressed by making content of BaO into the said range.

In the optical glass of the present embodiment, the total content of Li ₂ O, Na ₂ O, K ₂ O, and Cs ₂ O (hereinafter, may be described as “R ₂ O”) is 8 to 28%. Li ₂ O, Na ₂ O, K ₂ O, and Cs ₂ O are components that function to improve glass meltability. When R ₂ O is less than 8%, the meltability decreases, unmelted raw material remains easily, the viscosity of the molten glass becomes too high, the fluidity of the molten glass decreases, and the yield of glass per unit time decreases. On the other hand, when R ₂ O is more than 28%, the viscosity of the molten glass decreases, and the melting tank made of refractory materials such as bricks is easily corroded by the molten glass.

Therefore, the lower limit of R ₂ O is preferably 9%, and more preferably 10%, 12%, and 13% in this order. From the viewpoint of suppressing corrosion of refractory materials, the upper limit of R ₂ O is preferably 26%, more preferably 24%, and still more preferably 22%. By making _R2O into the said range, meltability and productivity of glass can be maintained.

In _{the optical glass of} this _{embodiment , the mass ratio} [ _{SiO 2 /} (SiO ₂ +B ₂ O ₃ +P ₂ O ₅ )] is 0.90 or more. In the optical glass of this embodiment, the network-forming component is mainly SiO ₂ . Compared with the content of B ₂ O ₃ and P ₂ O ₅ that can be used as network-forming components other than SiO ₂ , the content of SiO ₂ is extremely high. many.

Therefore, the lower limit of the mass ratio [SiO ₂ /(SiO ₂ +B ₂ O ₃ +P ₂ O ₅ )] is preferably 0.95, more preferably 0.98. The upper limit of the mass ratio is preferably 1. This mass ratio may also be 1. By making this mass ratio into the said range, the said desired property can be acquired.

In the optical glass of this embodiment, the mass ratio [SiO ₂ /R ₂ O] of the content of SiO ₂ to the total content of Li ₂ O, Na ₂ O, K ₂ O, and Cs ₂ O in R ₂ O is 1.5 to 3.2 . When the mass ratio is less than 1.5, the erosion of the refractory material by the molten glass becomes stronger, and the particulate refractory material from the wall surface of the eroded melting tank tends to mix into the molten glass and contaminate the glass, shortening the life of the melting tank. On the other hand, when the mass ratio is greater than 3.2, meltability decreases, unmelted raw materials tend to remain, the viscosity of the molten glass becomes too high, and the production of glass per unit time tends to decrease.

Therefore, the lower limit of the mass ratio [SiO ₂ /R ₂ O] is preferably 1.7, and more preferably 1.9, 2.1, and 2.3 in this order. In addition, the upper limit of the mass ratio is preferably 3.1, more preferably 3.0. By making this mass ratio into the said range, corrosion of a refractory material by a molten glass can be suppressed, and also the fall of a meltability can be suppressed.

In the optical glass of this embodiment, the mass ratio of the total content of SiO ₂ and R ₂ O (SiO ₂ +R ₂ O) to the total content of TiO ₂ and Nb ₂ O ₅ (TiO ₂ +Nb ₂ O ₅ ) [(SiO ₂ +R ₂ O)/(TiO ₂ +Nb ₂ O ₅ )] is 2.6 or less. Among the glass components, TiO ₂ and Nb ₂ O ₅ have a stronger effect of increasing the refractive index, while SiO ₂ and alkali metal oxides have a weaker effect of increasing the refractive index than TiO ₂ and Nb ₂ O ₅ .

Therefore, the upper limit of the mass ratio [(SiO ₂ +R ₂ O)/(TiO ₂ +Nb ₂ O ₅ )] is preferably 2.5, more preferably 2.3, further preferably 2.1. In addition, the lower limit of the mass ratio is preferably 1.4, more preferably 1.5, further preferably 1.6. Glass with a high refractive index can be obtained by making this mass ratio into the said range.

In the optical glass of this embodiment, the mass ratio of the content of TiO ₂ to the total content of TiO ₂ , Nb ₂ O ₅ and ZrO ₂ (TiO ₂ +Nb ₂ O ₅ +ZrO ₂ ) [TiO ₂ /(TiO ₂ + Nb ₂ O ₅ +ZrO ₂ )] is 0.90 or more. The lower limit of the mass ratio is preferably 0.95, more preferably 0.98. The upper limit of the mass ratio is preferably 1. This mass ratio may also be 1. Among TiO ₂ , Nb ₂ O ₅ , and ZrO ₂ that have a strong effect of increasing the refractive index, TiO ₂ is relatively less likely to increase the specific gravity. By setting this mass ratio within the above-mentioned range, an increase in specific gravity can be suppressed while obtaining a desired refractive index.

In the optical glass of this embodiment, the mass ratio of the total content of CaO and BaO (CaO+BaO) to the total content of MgO, CaO, SrO, and BaO (R'O) [(CaO+BaO)/R'O] 0.90 or more. The lower limit of the mass ratio is preferably 0.95, more preferably 0.98. The upper limit of the mass ratio is preferably 1. This mass ratio may also be 1. Among the alkaline earth metal oxides, CaO and BaO are components capable of maintaining the thermal stability of the glass strongly by introducing an appropriate amount. The thermal stability of glass can be maintained by making this mass ratio into the said range. Moreover, in the optical glass of this Embodiment, increase of a specific gravity can be suppressed by making the said mass ratio into the said range, reducing content of BaO.

In the optical glass of the present embodiment, the mass ratio [(Na ₂ O+K ₂ O)/R ₂ O] of the total content of Na ₂ O and K ₂ O to R ₂ O is 0.98 or more. The lower limit of the mass ratio is preferably 0.99. The upper limit of the mass ratio is preferably 1. This mass ratio may also be 1. Among the alkali metal oxides, Li ₂ O has a relatively strong erosive effect on refractory materials, and Cs ₂ O tends to increase its specific gravity compared with other alkali metal oxides. Among the alkali metal oxides, Na ₂ O and K ₂ O are superior in the function of maintaining the thermal stability of the glass. Therefore, by making this mass ratio into the said range, corrosion to a refractory material and increase in specific gravity can be suppressed, and the thermal stability of glass can be maintained.

In the optical glass of the present embodiment, the mass ratio [BaO/(Na ₂ O+K ₂ O+CaO)] of the content of BaO to the total content of Na ₂ O, K ₂ O, and CaO is 0.15 or less. The upper limit of the mass ratio is preferably 0.12, more preferably 0.10. The lower limit of the mass ratio is preferably zero. This mass ratio may also be zero. Na ₂ O, K ₂ O, and CaO have the effect of improving glass meltability. In addition, BaO is a component that increases the specific gravity. Therefore, by setting this mass ratio within the above-mentioned range, the meltability can be improved, and the increase in specific gravity can also be suppressed.

In the optical glass of the present embodiment, the mass ratio [BaO/(TiO ₂ +Nb ₂ O ₅ )] of the content of BaO to the total content of TiO ₂ and Nb ₂ O ₅ is 0.12 or less. The upper limit of the mass ratio is preferably 0.10, more preferably 0.08. The lower limit of the mass ratio is preferably zero. This mass ratio may also be zero. TiO ₂ and Nb ₂ O ₅ are components that impart high refractive index and high dispersion characteristics. In addition, BaO is a component that increases the specific gravity. Therefore, by setting this mass ratio within the above-mentioned range, it is possible to suppress an increase in specific gravity while maintaining desired high-refractive-index high-dispersion characteristics.

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

In the optical glass of the present embodiment, the upper limit of the mass ratio [(CaO+TiO ₂ )/SiO ₂ ] of the total content of CaO and TiO ₂ to the content of SiO ₂ is preferably 1.10, more preferably 1.08, still more preferably is 1.07. The lower limit of the mass ratio is preferably 0.90, more preferably 0.92, further preferably 0.93. From the viewpoint of obtaining glass with good thermal stability, the mass ratio is preferably in the above-mentioned range.

In the optical glass of this embodiment, the upper limit of the total content (R'O) of MgO, CaO, SrO, and BaO is preferably 20%, and more preferably 16%, 14%, and 12% in this order. In addition, the lower limit of R'O is preferably 2%, and more preferably 4%, 5%, and 6% in this order. From the viewpoint of improving meltability and suppressing a decrease in thermal stability, R'O is preferably in the above range.

In the optical glass of the present embodiment, the upper limit of the mass ratio [BaO/CaO] of the content of BaO to the content of CaO is preferably 0.30, and more preferably 0.28 and 0.26 in this order. In addition, the lower limit of the mass ratio is preferably zero. This mass ratio may also be zero. From the viewpoint of suppressing an increase in specific gravity, the mass ratio is preferably within the above-mentioned range.

Like Na ₂ O, K ₂ O functions to improve the meltability of the glass and to adjust the viscosity of the molten glass to an appropriate range. When too much K ₂ O is introduced, the refractive index may decrease and the aggressiveness of the molten glass may increase. The upper limit of the content of K ₂ O is preferably 7%, more preferably 6%, further preferably 5%. The lower limit of the content of K ₂ O is preferably 0%. Preferably, the K ₂ O content represented by mass % is less than the Na ₂ O content.

Li ₂ O is a component that functions to improve glass meltability. However, _Li2O is easy to attack refractory materials compared with other alkali metal oxides. Therefore, the range of the content of Li ₂ O is preferably 0-3%, more preferably 0-2%, further preferably 0-1%. The content of Li ₂ O may also be 0%.

Cs ₂ O tends to increase the specific gravity compared with other alkali metal oxides. In addition, the raw material cost of Cs ₂ O is high. Therefore, the range of the Cs ₂ O content is preferably 0-5%, more preferably 0-3%, and further preferably 0-1%. The content of Cs ₂ O may also be 0%.

CaO has the function of improving the thermal stability and melting property of glass, and adjusting the Abbe number. When CaO is excessive, thermal stability of glass will fall and a refractive index will fall. The upper limit of the content of CaO is preferably 15%, more preferably 13%, further preferably 12%. In addition, the lower limit of the content of CaO is preferably 3%, more preferably 5%, further preferably 6%.

Like CaO and BaO, MgO and SrO have the effect of improving the meltability, but the thermal stability of the glass is lowered even if the content of any component is excessive. The range of MgO content is preferably 0-10%, more preferably 0-5%, further preferably 0-3%. The MgO content may also be 0%. The range of the SrO content is preferably 0-10%, more preferably 0-5%, further preferably 0-3%. The content of SrO may also be 0%.

From the viewpoint of obtaining the above properties and characteristics, the total content of SiO ₂ , TiO ₂ , Na ₂ O, K ₂ O, CaO, and BaO is preferably at least 96%, more preferably at least 99%, and still more preferably at least 99.5%. above.

In the optical glass of the present embodiment, the upper limit of the content of P ₂ O ₅ is preferably 10%, and more preferably 8%, 5%, and 3% in this order. In addition, the lower limit of the content of P ₂ O ₅ is preferably 0%. The content of P ₂ O ₅ may also be 0%. In order to obtain optical glass with high refractive index and reduced specific gravity, the content of P ₂ O ₅ is preferably in the above range.

In the optical glass of the present embodiment, the upper limit of the content of B ₂ O ₃ is preferably 10%, and more preferably 8%, 5%, and 3% in this order. In addition, the lower limit of the content of B ₂ O ₃ is preferably 0%. The content of B ₂ O ₃ may also be 0%. Although B ₂ O ₃ has the effect of improving the thermal stability of glass, when the content of B ₂ O ₃ is too much, the refractive index will decrease. Therefore, the content of B ₂ O ₃ is preferably in the above range.

In the optical glass of this embodiment, the upper limit of the content of Al ₂ O ₃ is preferably 10%, and more preferably 8%, 5%, 3%, 1%, and 0.5% in this order. The lower limit of the content of Al ₂ O ₃ is preferably 0%. The content of Al ₂ O ₃ may also be 0%. Al ₂ O ₃ has the effect of improving chemical durability, but when the content of Al ₂ O ₃ is too large, the melting property of glass will deteriorate. Therefore, the content of Al ₂ O ₃ is preferably in the above range.

In the optical glass of the present embodiment, the upper limit of the content of ZrO ₂ is preferably 10%, and more preferably 8%, 5%, 3%, 1%, and 0.5% in this order. The lower limit of the content of ZrO ₂ is preferably 0%. The content of ZrO ₂ can also be 0%. ZrO ₂ is a component that imparts a high refractive index. On the other hand, when the content of ZrO ₂ is too large, the thermal stability decreases, and in addition, the specific gravity increases. Therefore, the content of _ZrO2 is preferably in the above range.

In the optical glass of the present embodiment, the upper limit of the content of Nb ₂ O ₅ is preferably 10%, and more preferably 8%, 5%, and 3% in this order. The lower limit of the content of Nb ₂ O ₅ is preferably 0%. The content of Nb ₂ O ₅ may also be 0%.

Nb ₂ O ₅ is a component that imparts a high refractive index and functions to improve the stability of the glass. On the other hand, when the content of Nb ₂ O ₅ is too large, the specific gravity increases and the thermal stability decreases. Therefore, the content of Nb ₂ O ₅ is preferably in the above range.

In the optical glass of this embodiment, the upper limit of the content of WO ₃ is preferably 10%, and more preferably 8%, 5%, and 3% in this order. The lower limit of the WO ₃ content is preferably 0%. The content of WO ₃ can also be 0%.

WO ₃ is a component that imparts a high refractive index. On the other hand, when the content of WO ₃ is too large, the thermal stability decreases and the specific gravity increases. In addition, the coloring of the glass increases and the transmittance decreases. Therefore, the content of WO ₃ is preferably in the above range.

In the optical glass of the present embodiment, the upper limit of the content of Bi ₂ O ₃ is preferably 10%, and more preferably 8%, 5%, and 3% in this order. In addition, the lower limit of the content of Bi ₂ O ₃ is preferably 0%. The content of Bi ₂ O ₃ may also be 0%.

By containing an appropriate amount of Bi ₂ O ₃ , it can improve the thermal stability of glass. In addition, Bi ₂ O ₃ is a component for achieving a high refractive index. On the other hand, when the content of Bi ₂ O ₃ is too large, the specific gravity increases. Furthermore, the coloring of glass will increase. Therefore, the content of Bi ₂ O ₃ is preferably in the above range.

In the optical glass of the present embodiment, the upper limit of the ZnO content is preferably 10%, and more preferably 8%, 5%, and 3% in this order. In addition, the lower limit of the content of ZnO is preferably 0%. The content of ZnO may also be 0%.

ZnO is a glass component that functions to improve the thermal stability of glass. However, when the content of ZnO is too large, the specific gravity will increase. Therefore, from the viewpoint of improving the thermal stability of the glass and maintaining desired optical properties, the content of ZnO is preferably within the above-mentioned range.

In the optical glass of the present embodiment, the upper limit of the content of Ta ₂ O ₅ is preferably 10%, and more preferably 8%, 5%, and 3% in this order. In addition, the lower limit of the content of Ta ₂ O ₅ is preferably 0%. The content of Ta ₂ O ₅ may also be 0%.

Ta ₂ O ₅ is a component that contributes to increasing the refractive index. In addition, Ta ₂ O ₅ is a glass component that functions to improve the thermal stability of glass. On the other hand, when the content of Ta ₂ O ₅ is too high, the thermal stability of the glass decreases, and when the glass is melted, unmelted glass raw material remains easily. In addition, the specific gravity will increase. Therefore, the content of Ta ₂ O ₅ is preferably in the above range.

In the optical glass of the present embodiment, the upper limit of the content of La ₂ O ₃ is preferably 10%, and more preferably 8%, 5%, and 3% in this order. In addition, the lower limit of the content of La ₂ O ₃ is preferably 0%. The content of La ₂ O ₃ may also be 0%.

La ₂ O ₃ is a component that contributes to increasing the refractive index. On the other hand, when the content of La ₂ O ₃ increases, the specific gravity increases and the thermal stability of the glass decreases. Therefore, from the viewpoint of suppressing an increase in specific gravity and a decrease in the thermal stability of the glass, the content of La ₂ O ₃ is preferably within the above-mentioned range.

In the optical glass of the present embodiment, the upper limit of the content of Y ₂ O ₃ is preferably 10%, and more preferably 8%, 5%, and 3% in this order. In addition, the lower limit of the content of Y ₂ O ₃ is preferably 0%. The content of Y ₂ O ₃ may also be 0%.

Y ₂ O ₃ is a component that contributes to increasing the refractive index. On the other hand, when the content of Y ₂ O ₃ is too high, the thermal stability of the glass decreases, and the glass tends to devitrify during the manufacturing process. Therefore, the content of Y ₂ O ₃ is preferably within the above-mentioned range from the viewpoint of suppressing a decrease in the thermal stability of the glass.

In the optical glass of this 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%. The content of Sc ₂ O ₃ may also be 0%.

In the optical glass of this embodiment, the content of HfO ₂ is preferably 2% or less. In addition, the lower limit of the content of HfO ₂ is preferably 0%. The content of HfO ₂ can also be 0%.

Sc ₂ O ₃ and HfO ₂ have an effect of improving the high dispersion of glass, but they are expensive components. Therefore, the respective contents of Sc ₂ O ₃ and HfO ₂ are preferably in the above-mentioned ranges.

In the optical glass of this 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%. The content of Lu ₂ O ₃ may also be 0%.

Lu ₂ O ₃ is a glass component that increases the specific gravity of glass because of its large molecular weight, although it has the effect of improving the high dispersion of glass. Therefore, the content of Lu ₂ O ₃ is preferably in the above range.

In the optical glass of this embodiment, the content of GeO ₂ is preferably 2% or less. In addition, the lower limit of the content of GeO ₂ is preferably 0%. The content of GeO ₂ may also be 0%.

GeO ₂ has an effect of improving the high dispersion of glass, but it is a very expensive component among commonly used glass components. Therefore, from the viewpoint of reducing the manufacturing cost of glass, the content of GeO ₂ is preferably in the above-mentioned range.

In the optical glass of this embodiment, the upper limit of the content of Gd ₂ O ₃ is preferably 3.0%, more preferably 2.0%. In addition, the lower limit of the content of Gd ₂ O ₃ is preferably 0%. The content of Gd ₂ O ₃ may also be 0%.

Gd ₂ O ₃ is a component that contributes to increasing the refractive index. On the other hand, when the content of Gd ₂ O ₃ is too large, the thermal stability of glass decreases. In addition, when the content of Gd ₂ O ₃ is too large, the specific gravity of glass increases, which is not preferable. Therefore, the content of Gd ₂ O ₃ is preferably in the above range from the viewpoint of maintaining good thermal stability of the glass and suppressing an increase in specific gravity.

In the optical glass of this embodiment, the content of Yb ₂ O ₃ is preferably 2% or less. In addition, the lower limit of the content of Yb ₂ O ₃ is preferably 0%. The content of Yb ₂ O ₃ may also be 0%.

Yb ₂ O ₃ is a component that increases the specific gravity of glass. In addition, when the content of Yb ₂ O ₃ is too large, the thermal stability of glass decreases. The content of Yb ₂ O ₃ is preferably within the above-mentioned range from the viewpoint of preventing a decrease in the thermal stability of the glass and suppressing an increase in specific gravity.

The optical glass of this embodiment is preferably mainly composed of the above-mentioned glass components, that is, SiO ₂ , TiO ₂ , and Na ₂ O as essential components, and BaO, K ₂ O, Li ₂ O, and Cs ₂ O as optional components. , CaO, MgO, SrO, P ₂ O ₅ , B ₂ O ₃ , Al ₂ O ₃ , ZrO ₂ , Nb ₂ O ₅ , WO ₃ , Bi ₂ O ₃ , ZnO, Ta ₂ O ₅ , La ₂ O ₃ , Composed of Y ₂ O ₃ , Sc ₂ O ₃ , HfO ₂ , Lu ₂ O ₃ , GeO ₂ , Gd ₂ O ₃ and Yb ₂ O ₃ , the total content of the above glass components is preferably at least 95%, more preferably 98% Above, more preferably 99% or more, still more preferably 99.5% or more.

The optical glass of the present embodiment is preferably composed basically of the glass components described above, but may contain other components within a range that does not impair the effects of the present invention. Furthermore, in the present invention, inclusion of unavoidable impurities is not excluded.

(Other components) The optical glass of this embodiment can contain a small amount of _Sb2O3 , _{CeO2 ,} etc. as a clarifier other than the said component. In addition, in this specification, content of a clarifying agent is shown by a ratio other than a ratio, and is not included in the total content of all glass components shown on an oxide basis. Therefore, when the total content of all glass components other than the clarifier is 100% by mass, the total amount of the clarifier is preferably 1% by mass or less, more preferably 0.5% by mass or less, or 0.1% by mass or less. The content of clarifying agent can also be 0%.

Pb, Cd, As, Th, etc. are components that affect the environment. Therefore, each content of PbO, CdO, and _ThO is preferably 0-0.1%, more preferably 0-0.05%, further preferably 0-0.01%, and particularly preferably does not contain PbO, CdO, or ThO substantially. ₂ .

The content of As ₂ O ₃ is preferably 0-0.1%, more preferably 0-0.05%, further preferably 0-0.01%, and particularly preferably does not contain As ₂ O ₃ substantially.

Furthermore, the optical glass of the present embodiment can obtain high transmittance over a wide range of the visible light region. In order to make use of this characteristic, it is preferable not to contain a coloring element. Cu, Co, Ni, Fe, Cr, Eu, Nd, Er, etc. can be illustrated as a coloring element. Regardless of any element, it is preferably less than 100 mass ppm, more preferably 0 to 80 mass ppm, further preferably 0 to 50 mass ppm, and particularly preferably not substantially containing these elements.

In addition, Ga, Te, Tb, etc. are components that do not need to be introduced and are also expensive components. Therefore, the respective content ranges of Ga ₂ O ₃ , TeO ₂ , and TbO ₂ represented by mass % are preferably 0-0.1%, more preferably 0-0.05%, further preferably 0-0.01%, and even more preferably It is preferably 0 to 0.005%, further preferably 0 to 0.001%, and particularly preferably does not substantially contain these components.

(glass characteristics) [Abbe number νd, refractive index nd] In the optical glass of this embodiment, from the viewpoint of correcting chromatic aberration by combining it with a lens made of glass having other optical characteristics, the Abbe number νd is preferably 26 or more, more preferably 26.5 or more, still more preferably 27 or more. The upper limit of Abbe's number νd is preferably 33, more preferably 32.5, and still more preferably 32.

Optical glass with a high refractive index nd is desired because it can have the same light-gathering ability and can reduce the absolute value of the curvature of the optically functional surface of the lens (slow down the curve of the optically functional surface of the lens). In the optical glass of this embodiment, the lower limit of the refractive index nd is preferably 1.67, more preferably 1.675, and still more preferably 1.68.

On the other hand, when the refractive index is too high, the relative ratio of the high refractive index component becomes high, and the specific gravity of glass increases. From the viewpoint of suppressing an increase in specific gravity, in the optical glass of the present embodiment, the upper limit of the refractive index nd is preferably 1.77, more preferably 1.765, and still more preferably 1.76.

[Transmittance] The optical glass of this embodiment may be optical glass with very little coloring. This optical glass is suitably used as a material for imaging optical elements such as camera lenses and projection optical elements such as projectors.

The coloring degree of general optical glass is represented by λ80, λ70, λ5, etc. Measure the spectral transmittance of a glass sample with a thickness of 10.0mm±0.1mm within the wavelength range of 200~700, set the wavelength at which the external transmittance is 80% as λ80, and the wavelength at which the external transmittance is 70% as λ70, The wavelength at which the external transmittance is 5% is set to λ5. The optical glass of the present embodiment preferably has λ80 of 480 nm or less, λ70 of 440 nm or less, and λ5 of 380 nm or less.

[Glass transition temperature Tg] The glass transition temperature Tg of the optical glass of the present embodiment is preferably 640° C. or lower. When the glass transition temperature is low, the heating temperature at the time of reheating, softening, and press-molding the glass can be lowered. As a result, fusion of the glass and the press-molding mold is easily suppressed. In addition, since the heating temperature can be lowered, it is possible to reduce heat consumption of a glass heating device, a press molding die, and the like. Furthermore, since the annealing temperature of glass can also be lowered, the lifetime of an annealing furnace can be extended. The glass transition temperature is more preferably at most 635°C, further preferably at most 630°C.

[proportion] The specific gravity of the optical glass of this embodiment is preferably 3.40 or less. The specific gravity is more preferably 3.20 or less, further preferably 3.10 or less, particularly preferably 3.00 or less.

[use] A preferred mode of the optical glass of the present embodiment is optical glass for optical lenses or optical glass for glass.

[Manufacturing method] The optical glass of the present embodiment can be obtained, for example, by preparing, melting, and molding glass raw materials to obtain desired characteristics. As glass raw materials, oxides, carbonates, nitrates, sulfates, etc. can be used, for example. Known methods can be used as the melting method and molding method of glass.

[Glass raw material for press molding, method for manufacturing same, and method for manufacturing glass molding] According to one aspect of the present invention, a press-molding glass raw material composed of the optical glass of the present embodiment, a glass molded article composed of the optical glass of the present embodiment, and methods for producing them can be provided. The press-molding of the glass raw material for press-molding can be performed by the method of pressing the glass raw material for press-molding which was heated and softened using the press-molding mold. Both heating and press molding can be performed in an air environment. Coating the powdered release agent such as boron nitride evenly on the surface of the glass raw material for press molding, heating and press molding can reliably prevent the fusion of the glass and the molding mold, and can follow the molding process of the press molding mold. The surface stretches the glass smoothly. By annealing after press molding to reduce the strain inside the glass, a homogeneous optical element blank can be obtained.

Examples of glass raw materials for press molding include preforms for precision press molding, glass raw materials for press molding optical element blanks (glass gobs for press molding), etc. glass blocks of comparable quality.

In addition, glass raw materials for press molding are also referred to as preforms, and include not only those directly supplied to press molding but also those supplied to press molding by mechanical processing such as cutting, grinding, and polishing. The cutting method includes: forming a groove by a scribing method on a portion of the surface of the glass plate to be cut, and applying local pressure to the groove portion on the back side of the surface where the groove is formed to cut the glass plate at the groove portion, Or the method of cutting the glass plate with a cutting blade. Moreover, as a polishing method, spherical surface processing using a curve generator (curve generator), smoothing processing, etc. are mentioned. As a polishing method, a method of polishing using abrasive grains such as cerium oxide and zirconia is mentioned.

[Optical element blank and manufacturing method thereof] According to 1 aspect of this invention, the optical element blank which consists of the optical glass of this embodiment can be provided. An optical element blank is a glass molded body having a shape similar to that of an optical element to be produced. The optical element blank can be produced by a method such as molding into a shape in which a machining allowance removed during processing is added to the shape of the optical element to be produced. For example, a method of heating and softening a glass raw material for press molding and press molding (reheat press method), a method of press molding by supplying a molten glass gob to a press molding mold by a known method (direct press method) ) etc. to make optical element blanks.

[Optical element and its manufacturing method] According to 1 aspect of this invention, the optical element comprised from the optical glass of this embodiment can be provided. Examples of the type of optical element include lenses such as spherical lenses and aspheric lenses, lenses, 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. An optical element can be manufactured by the method including the process of processing the glass molded object comprised from the optical glass of this embodiment. As processing, dicing, cutting, rough grinding, finish grinding, polishing and the like can be exemplified. By using the above-mentioned glass when performing such processing, damage can be reduced and high-quality optical elements can be stably provided. [Example]

Hereinafter, the present invention will be further described in detail by means of examples. However, the present invention is not limited to the aspects shown in the examples.

(Example 1) In order to form the glass compositions shown in Table 1 (1) to (3), the oxides corresponding to each are used as the raw materials for introducing each component, and the raw materials are weighed and mixed thoroughly to prepare the blended raw materials.

This prepared raw material was put into a crucible made of platinum, and heated and melted. After melting, the molten glass is introduced into a mold, cooled to around the glass transition temperature, and immediately placed in an annealing furnace, annealed at around the glass transition temperature for about 1 hour, and then cooled to room temperature in the furnace, thereby Optical glass having a composition shown in Table 1 (1) to (3) was obtained.

When the obtained optical glass was observed under magnification with an optical microscope, precipitation of crystals, foreign matter such as platinum particles originating from a platinum crucible, bubbles, and lines were not observed.

Each characteristic of the obtained optical glass was measured by the method shown below. The results are shown in Table 2.

(i) Refractive index nd, ng, nF, nC and Abbe's number νd For glass obtained by cooling at a cooling rate of -30°C/hour, the refractive index was measured in accordance with the standard refractive index measurement method of the Japan Optical Glass Industry Association. nd, ng, nF, nC, calculate the Abbe number νd based on formula (1).

(ii) Transmittance (λ80, λ70, and λ5) Measure the spectral transmittance of a sample with a thickness of 10.0mm±0.1mm within the wavelength range of 200~700nm. The wavelength at which the external transmittance is 80% is λ80, the wavelength at which the external transmittance is 70% is λ70, and the wavelength at which the external transmittance is 5% is λ5.

(iii) Glass transition temperature Tg The measurement was performed at a temperature increase rate of 10°C/min using a differential scanning calorimeter (DSC3300) manufactured by NETZSCH.

(iv) specific gravity Measurement was performed according to the Archimedes method.

[Table 1(1)] Glass composition (mass%) No. SiO ₂ Na ₂ O K ₂ O CaO BaO Nb ₂ O ₅ TiO ₂ total Sb ₂ O ₃ 1 42.73 15.08 0.00 7.39 1.70 0.00 33.10 100.00 0.10 2 43.19 15.25 0.00 8.10 0.00 0.00 33.46 100.00 0.10 3 44.03 14.62 0.00 8.06 0.00 0.00 33.29 100.00 0.10 4 43.01 14.63 0.00 9.05 0.00 0.00 33.31 100.00 0.10 5 42.82 14.57 0.00 8.03 0.00 0.00 34.58 100.00 0.10 6 41.97 14.64 0.00 10.05 0.00 0.00 33.34 100.00 0.10 7 42.05 14.66 0.00 10.44 0.00 0.00 32.85 100.00 0.10 8 41.19 15.29 0.00 10.50 0.00 0.00 33.02 100.00 0.10 9 42.81 14.02 0.00 10.00 0.00 0.00 33.17 100.00 0.10 10 42.88 14.04 0.00 10.36 0.00 0.00 32.72 100.00 0.10 11 42.04 14.66 0.00 10.41 0.00 0.00 32.89 100.00 0.10

[Table 1(2)] Glass composition (mass%) No. (SiO ₂ +R ₂ O) /(TiO ₂ +Nb ₂ O ₅ ) TiO ₂ / (TiO ₂ +Nb ₂ O ₅ +ZrO ₂ ) Li ₂ O+Na ₂ O+K ₂ O+Cs ₂ O (=R ₂ O) MgO+CaO+SrO+BaO (=R'O) SiO ₂ /R ₂ O (CaO+TiO ₂ )/ SiO ₂ 1 1.75 1.00 15.08 9.09 2.83 0.95 2 1.75 1.00 15.25 8.10 2.83 0.96 3 1.76 1.00 14.62 8.06 3.01 0.94 4 1.73 1.00 14.63 9.05 2.94 0.98 5 1.66 1.00 14.57 8.03 2.94 1.00 6 1.70 1.00 14.64 10.05 2.87 1.03 7 1.73 1.00 14.66 10.44 2.87 1.03 8 1.71 1.00 15.29 10.50 2.69 1.06 9 1.71 1.00 14.02 10.00 3.05 1.01 10 1.74 1.00 14.04 10.36 3.05 1.00 11 1.72 1.00 14.66 10.41 2.87 1.03

[Table 1(3)] Glass composition (mass%) No. (CaO+BaO) /R'O SiO ₂ / (SiO ₂ +B ₂ O ₃ +P ₂ O ₅ ) (Na ₂ O+K ₂ O) /R ₂ O BaO/CaO BaO/ ( _Na2O + _K2O +CaO) BaO/ (TiO ₂ +Nb ₂ O ₅ ) 1 1.00 1.00 1.00 0.23 0.08 0.05 2 1.00 1.00 1.00 0.00 0.00 0.00 3 1.00 1.00 1.00 0.00 0.00 0.00 4 1.00 1.00 1.00 0.00 0.00 0.00 5 1.00 1.00 1.00 0.00 0.00 0.00 6 1.00 1.00 1.00 0.00 0.00 0.00 7 1.00 1.00 1.00 0.00 0.00 0.00 8 1.00 1.00 1.00 0.00 0.00 0.00 9 1.00 1.00 1.00 0.00 0.00 0.00 10 1.00 1.00 1.00 0.00 0.00 0.00 11 1.00 1.00 1.00 0.00 0.00 0.00

[Table 2] Glass properties No. proportion nd νd λ80(nm) λ70(nm) λ5(nm) Tg( °C) 1 2.95 1.73563 28.08 450 417 367 614 2 2.92 1.73492 28.06 443 413 367 618 3 2.92 1.73391 28.07 445 414 367 623 4 2.93 1.73748 28.09 445 413 367 627 5 2.93 1.74405 27.40 449 416 369 628 6 2.94 1.74070 28.12 449 415 367 629 7 2.94 1.73818 28.40 447 414 366 626 8 2.95 1.73905 28.38 445 414 366 624 9 2.94 1.73975 28.17 446 413 367 632 10 2.93 1.73747 28.41 441 411 367 622 11 2.94 1.73849 28.37 443 413 367 621

(Example 2) Using a glass melting furnace with a melting tank made of a refractory material, a clarification tank made of a platinum alloy, and a working tank (stirring tank), batches of raw materials prepared so as to obtain the optical glasses produced in Example 1 were put into In the melting tank, glass is melted.

Batches of raw materials are melted into molten glass in the melting tank. Through the pipeline connecting the melting tank and the clarification tank, and the pipeline connecting the clarification tank and the working tank, the melting tank flows into the clarification tank, and the clarification tank flows into the working tank. In the process After clarification and homogenization, it flows into the molding mold through the outflow pipe installed at the bottom of the working tank.

Glass is formed in a mold, and the formed glass is annealed to obtain optical glass. The obtained optical glass was observed, and it was confirmed that there were no unmelted residues of raw materials, contamination of refractory materials, and precipitation of crystals.

Each of the optical glasses obtained in Example 1 was produced using a continuous type glass melting furnace in this way. In addition, the above-mentioned glass melting furnace has a known structure.

(Example 3) Using each optical glass produced in Example 2, a lens blank was produced by a known method, and the lens blank was processed by a known method such as polishing to produce various lenses.

The optical lenses produced are biconvex lenses, biconcave lenses, plano-convex lenses, plano-concave lenses, concave meniscus lenses and convex meniscus lenses and other lenses.

Since glass has a low specific gravity, each lens is lighter than a lens having the same optical characteristics and dimensions, and is suitable for various imaging devices, especially autofocus type imaging devices because energy can be saved. Similarly, various optical glasses produced in Example 2 were used to produce 稜鏡.

It should be understood that the embodiments disclosed this time are illustrative in any respect and do not limit the present invention. The scope of the present invention is shown by the scope of the claims rather than the above-described description, and it is intended to include all changes within the range having the equivalent meaning and the scope of the claims.

For example, the optical glass of one aspect of the present invention can be produced by performing the component adjustment described in the specification about the glass composition shown above. In addition, of course, it is also possible to arbitrarily combine two or more items described as examples or preferred ranges in the specification.

none

none.

Claims (4)

An optical glass, represented by mass %, the content of SiO ₂ is 20-51%, the content of TiO ₂ is 20-40%, the content of Na ₂ O is 5-28%, the content of BaO is less than 2.0%, and the content of Li ₂ O , Na ₂ O, K ₂ O and Cs ₂ O total content (R ₂ O) is 8~28%, SiO ₂ content and SiO ₂ , B ₂ O ₃ and P ₂ O ₅ total content (SiO ₂ + B ₂ O ₃ +P ₂ O ₅ ) mass ratio [SiO ₂ /(SiO ₂ +B ₂ O ₃ +P ₂ O ₅ )] is 0.90 or more, SiO ₂ content to R ₂ O mass ratio [SiO ₂ /R ₂ O] is 1.5~3.2, the mass of the total content of SiO ₂ and R ₂ O (SiO ₂ +R ₂ O) and the total content of TiO ₂ and Nb ₂ O ₅ (TiO ₂ +Nb ₂ O ₅ ) The ratio [(SiO ₂ +R ₂ O)/(TiO ₂ +Nb ₂ O ₅ )] is 2.6 or less, the content of TiO ₂ and the total content of TiO ₂ , Nb ₂ O ₅ and ZrO ₂ (TiO ₂ +Nb ₂ O ₅ + ZrO ₂ ) mass ratio [TiO ₂ /(TiO ₂ +Nb ₂ O ₅ +ZrO ₂ )] is 0.90 or more, the total content of CaO and BaO (CaO+BaO) and the total of MgO, CaO, SrO and BaO The mass ratio of content (R'O) [(CaO+BaO)/R'O] is 0.90 or more, and the mass ratio of the total content of Na ₂ O and K ₂ O to R ₂ O [(Na ₂ O+K ₂ O )/R ₂ O] is 0.98 or more, the mass ratio of BaO content to the total content of Na ₂ O, K ₂ O and CaO [BaO/(Na ₂ O+K ₂ O+CaO)] is 0.15 or less, BaO The mass ratio [BaO/(TiO ₂ +Nb ₂ O ₅ )] of the content to the total content of TiO ₂ and Nb ₂ O ₅ is 0.12 or less. According to the optical glass described in Claim 1, the refractive index nd is 1.67-1.77, and the Abbe number νd is 26-33. The optical glass according to claim 1 or 2, which has a specific gravity of 3.40 or less. An optical element, which is made of the optical glass described in any one of Claims 1-3.