TW202012329A - Optical glass, optical element blank and optical element having a refractive index nd being 1.70 to 1.85 - Google Patents

Abstract

Disclosed is an optical glass excellent in acid resistance, an optical element blank and an optical element. The refractive index nd of the optical glass is 1.70 to 1.85, the content of B2O3 is 5 to 35% by mass, the content of La2O3 is 25 to 50% by mass, and the content of Al2O3 is 1 to 20% by mass. The optical glass satisfies the following (a) or (b): (a) Abbe number [nu]d is 42 or more and less than 50, and the acid resistance based on JOGIS is grade1-2; (b) Abbe number [nu]d is 50 or more and 55 or less, and the acid resistance based on JOGIS is grade1-3.

Description

Optical glass, optical element blank and optical element

The present invention relates to an optical glass excellent in acid resistance, an optical element blank, and an optical element.

In recent years, with the improvement of image quality and resolution of digital cameras and the like, optical glass with low dispersion has been sought. Traditionally, such low dispersion optical glass has insufficient acid resistance. Therefore, in applications requiring high durability, such as in-vehicle use, further improvement is sought.

The optical glass disclosed in Patent Document 1 has low dispersion, but there is no concern about acid resistance. In addition, since 4% or more of fluorine (F) is contained as a glass component, the glass component easily volatilizes when the glass is melted, and the composition of the molten glass may be unstable.

[Prior Technical Literature] [Patent Literature] [Patent Document 1]: Japanese Patent Laid-Open No. 2014-214082.

[Problems to be solved by the invention]

In view of such a practical situation, an object of the present invention is to provide an optical glass, an optical element blank, and an optical element excellent in acid resistance.

[Proposal to solve the problem]

The inventors of the present invention conducted intensive research in order to achieve the above object, and as a result, found that by adjusting the content ratio of various glass constituent components (hereinafter referred to as "glass components") constituting the glass, this objective can be achieved based on this knowledge The present invention has been completed.

That is, the main content of the present invention is as follows.

(1) An optical glass with a refractive index nd of 1.70 to 1.85, a B ₂ O ₃ content of 5 to 35% by mass, a La ₂ O ₃ content of 25 to 50% by mass, and an Al ₂ O ₃ content of 1 -20% by mass, and the optical glass satisfies the following (a) or (b), (a) Abbe number νd is 42 or more and less than 50, acid resistance is graded 1 to 2 based on JOGIS, (b) Abbe The number νd is 50 or more and 55 or less, and the acid resistance based on JOGIS is 1 to 3 grades.

(2) An optical glass with a refractive index nd of 1.70 to 1.85, an Abbe number νd of 42 to 55, a content of SiO ₂ of 5 to 20% by mass, a content of B ₂ O ₃ of 5 to 35% by mass, La The content of ₂ O ₃ is 25-50% by mass, the content of Al ₂ O ₃ is 1-20% by mass, and the mass ratio of the content of B ₂ O _{3 to} the content of Al ₂ O ₃ [B ₂ O ₃ /Al ₂ O ₃ ] is 8 or less, and the content of F is added, and is 2% by mass or less.

(3) An optical element blank composed of the optical glass described in (1) or (2) above.

(4) An optical element comprising the optical element blank described in (3) above.

[Effect of invention]

According to the present invention, an optical glass, an optical element blank, and an optical element excellent in acid resistance can be provided.

Hereinafter, embodiments of the present invention will be described. In addition, in the present invention and the present specification, the glass composition of the optical glass is expressed on the basis of oxide unless otherwise specified. Here, the "oxide-based glass composition" refers to a glass composition obtained by converting all glass raw materials when they are melted and being present as oxides in optical glass, and the expression of each glass component is conventional It is written as SiO ₂ , TiO _2, etc. The content of the glass component and the total content are quality standards unless otherwise specified, and "%" means "mass %".

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

In addition, in this specification, unless otherwise specified, the refractive index refers to the refractive index nd of d line (wavelength 587.56 nm) of helium.

The Abbe number νd is used as a value indicating a property related to dispersion, and is expressed by the following formula. Here, nF is the refractive index of the blue hydrogen F line (wavelength 486.13 nm), and nC is the refractive index of the red hydrogen C line (656.27 nm). νd=(nd-1)/(nF-nC)

Hereinafter, the optical glass of the present invention will be described by dividing it 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, descriptions and overlapping matters related to the first embodiment are appropriately omitted.

First embodiment

The optical glass of the first embodiment of the present invention has a refractive index nd of 1.70 to 1.85, a B ₂ O ₃ content of 5 to 35%, a La ₂ O ₃ content of 25 to 50%, and an Al ₂ O ₃ content It is 1-20%. The optical glass is characterized by satisfying the following (a) or (b), (a) Abbe number νd is 42 or more and less than 50, and the acid resistance based on JOGIS is 1 to 2, ( b) Abbe number νd is 50 or more and 55 or less, and the acid resistance based on JOGIS is 1 to 3 grades.

Hereinafter, the optical glass of the first embodiment will be described in detail.

In the optical glass of the first embodiment, the refractive index nd is 1.70 to 1.85. The refractive index nd can also be set to 1.71 to 1.84, or 1.72 to 1.83.

The refractive index nd can be controlled by adjusting the composition of the glass composition. For example, the components that relatively increase the refractive index nd are Nb ₂ O ₅ , TiO ₂ , ZrO ₂ , Ta ₂ O ₅ , La ₂ O ₃ , Gd ₂ O ₃ , and Y ₂ O ₃ . The components that relatively reduce the refractive index nd are SiO ₂ , B ₂ O ₃ , Li ₂ O, Na ₂ O, and K ₂ O. The refractive index nd is controlled by appropriately adjusting the content of these components.

In the optical glass of the first embodiment, the content of B ₂ O ₃ is 5 to 35%. The upper limit of the content of B ₂ O ₃ is preferably 31%, and further preferably 29%, 27%, and 25%. In addition, the lower limit of the content of B ₂ O ₃ is preferably 7%, and further preferably 8%, 9%, and 10% in order.

When the content of B ₂ O ₃ is too large, the acid resistance may decrease. In addition, when the content of B ₂ O ₃ is too small, the thermal stability of the glass may decrease.

In the optical glass of the first embodiment, the content of La ₂ O ₃ is 25 to 50%. The upper limit of the content of La ₂ O ₃ is preferably 48%, and further preferably 46%, 44%, and 42%. In addition, the lower limit of the content of La ₂ O ₃ is preferably 27%, and further preferably 28%, 29%, and 30% in this order.

By setting the content of La ₂ O ₃ to the above range, the acid resistance of the glass can be improved, and the required optical constant can be achieved.

In the optical glass of the first embodiment, the content of Al ₂ O ₃ is 1 to 20%. The upper limit of the content of Al ₂ O ₃ is preferably 18%, and further preferably 16%, 15%, and 14%. In addition, the lower limit of the content of Al ₂ O ₃ is preferably 2%, and further preferably 3%, 4%, and 5% in this order.

When the content of Al ₂ O ₃ is too large, the liquidus temperature LT may increase, and it may become highly dispersive, and an optical glass having a desired optical constant cannot be obtained. In addition, when the content of Al ₂ O ₃ is too small, the acid resistance may decrease.

The optical glass of the first embodiment satisfies the following (a) or (b).

(a) Abbe number νd is 42 or more and less than 50, and the acid resistance based on JOGIS is 1 to 2 grades.

(b) Abbe number νd is 50 or more and 55 or less, and the acid resistance based on JOGIS is 1 to 3 grades.

In the case of (a) above, the Abbe number νd is 42 or more and less than 50. The Abbe number νd can also be set to 43 or more and less than 50 or 44 or more and less than 50.

Abbe number νd can be controlled by adjusting the composition of the glass composition. The components that relatively reduce the Abbe number νd are Nb ₂ O ₅ , TiO ₂ , ZrO ₂ , and Ta ₂ O ₅ . The components that relatively increase the Abbe number νd are SiO ₂ , B ₂ O ₃ , Li ₂ O, Na ₂ O, K ₂ O, La ₂ O ₃ , Gd ₂ O ₃ , Y ₂ O ₃ , BaO, CaO, SrO . Abbe number νd can be controlled by appropriately adjusting the content of these components.

Furthermore, in the case of (a) above, the acid resistance based on JOGIS is 1 to 2, and preferably 1 level. The acid resistance can be improved by appropriately adjusting the contents of B ₂ O ₃ and Al ₂ O ₃ .

In addition, the acid resistance was evaluated in accordance with the Japanese Optical Glass Industry Association standard JOGIS06-2009. Specifically, powder glass (particle size 425-600 μm) corresponding to a specific gravity is placed in a platinum cage, immersed in a round-bottom flask made of quartz glass containing a 0.01 mol/L nitric acid aqueous solution, and treated in a boiling water bath for 60 Minutes, the weight reduction rate Da (%) before and after the treatment was measured. Table 1 shows the grade of acid resistance weight reduction rate Da.

[Table 1] Table 1

In the case of (b) above, the Abbe number νd is 50 or more and 55 or less. The Abbe number νd can also be set to 50 or more and 54.5 or less or 50 or more and 54 or less. The glass composition related to the control of the Abbe number νd is the same as in the case of (a) above.

Furthermore, in the case of (b) above, the acid resistance based on JOGIS is 1 to 3 grades, preferably 1 to 2 grades, and more preferably 1 grade. The glass component related to the control of acid resistance is the same as the case of (a) above. In addition, the evaluation method of acid resistance is also the same as the case of (a) above.

In the optical glass of the first embodiment, the upper limit of the content of SiO ₂ is preferably 20%, and further preferably 17%, 14%, and 12%. In addition, the lower limit of the content of SiO ₂ is preferably 5%, and further preferably 6%, 7%, and 8%. By setting the content of SiO ₂ to the above range, it is possible to suppress the decrease in acid resistance, devitrification resistance, and chemical durability of the glass.

In the optical glass of the first embodiment, the upper limit of the mass ratio of the content of B ₂ O _{3 to} the content of Al ₂ O ₃ [B ₂ O ₃ /Al ₂ O ₃ ] is preferably 8, and in turn, it is more preferably 5, 4, 3. In addition, the lower limit of the mass ratio [B ₂ O ₃ /Al ₂ O ₃ ] is preferably 0.5, and further preferably 0.6, 0.7, and 0.8 in this order. By setting the mass ratio [B ₂ O ₃ /Al ₂ O ₃ ] to the above range, the decrease in acid resistance is suppressed, and an optical glass having a desired optical constant is obtained.

Hereinafter, the content, ratio, and glass characteristics of glass components other than the above in the optical glass of the first embodiment will be described in detail.

In 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 14.5%, and further preferably 14.8%, 15%, and 15.1% in this order. In addition, the upper limit of the total content [SiO ₂ +Al ₂ O ₃ ] is preferably 30%, and further preferably 28%, 27%, and 26% in order. By setting the total content [SiO ₂ +Al ₂ O ₃ ] to the above range, the required acid resistance and devitrification resistance can coexist.

In the optical glass of the first embodiment, the lower limit of the total content of SiO ₂ , B ₂ O _3, and Al ₂ O ₃ [SiO ₂ + B ₂ O ₃ + Al ₂ O ₃ ] is preferably 31.0%, and further preferably 31.5%, 32%, 32.5%. In addition, the upper limit of the total content [SiO ₂ +B ₂ O ₃ +Al ₂ O ₃ ] is preferably 45%, and further preferably 44%, 43%, and 42% in this order. By setting the total content [SiO ₂ +B ₂ O ₃ +Al ₂ O ₃ ] to the above range, the required acid resistance and devitrification resistance can coexist.

In the optical glass of the first embodiment, the lower limit of the mass ratio of the content of SiO _{2 to} the content of La ₂ O ₃ [SiO ₂ /La ₂ O ₃ ] is preferably 0.19, and more preferably 0.20, 0.21 in order. 0.22. In addition, the upper limit of the mass ratio [SiO ₂ /La ₂ O ₃ ] is preferably 0.34, and further preferably 0.32, 0.31, and 0.30. By setting the mass ratio [SiO ₂ /La ₂ O ₃ ] to the above range, the required acid resistance and devitrification resistance can coexist.

In the optical glass of the first embodiment, the lower limit of the mass ratio of the content of Al ₂ O _{3 to} the content of La ₂ O ₃ [Al ₂ O ₃ /La ₂ O ₃ ] is preferably 0.15, and is more preferably in order 0.16, 0.17, 0.18. In addition, the upper limit of the mass ratio [Al ₂ O ₃ /La ₂ O ₃ ] is preferably 0.40, and further preferably 0.39, 0.38, and 0.37 in this order. By setting the mass ratio [Al ₂ O ₃ /La ₂ O ₃ ] to the above range, the required acid resistance and devitrification resistance can coexist.

In the optical glass of the first embodiment, the mass ratio of the total content of SiO ₂ , B ₂ O ₃ and Al ₂ O _{3 to} the content of La ₂ O ₃ [(SiO ₂ + B ₂ O ₃ + Al ₂ O ₃ )/ The lower limit of La ₂ O ₃ ] is preferably 0.68, and further preferably 0.70, 0.72, and 0.74. In addition, the upper limit of the mass ratio [(SiO ₂ +B ₂ O ₃ +Al ₂ O ₃ )/La ₂ O ₃ ] is preferably 1.10, and further preferably 1.08, 1.06, and 1.04 in this order. By setting the mass ratio [(SiO ₂ +B ₂ O ₃ +Al ₂ O ₃ )/La ₂ O ₃ ] to the above range, the required acid resistance and devitrification resistance can coexist.

In the optical glass of the first embodiment, the upper limit of the content of P ₂ O ₅ is preferably 5%, and further preferably 4%, 3%, and 2% in this order. In addition, it is preferable that the content of P ₂ O ₅ is small, and the lower limit is preferably 0%. The content of P ₂ O ₅ may be 0%. By setting the content of P ₂ O ₅ to the above range, it is possible to suppress the decrease in the devitrification resistance and weather resistance of the glass.

In the optical glass of the first embodiment, the upper limit of the content of Li ₂ O is preferably 5%, and further preferably 4%, 3%, and 2% in this order. Preferably, the content of Li ₂ O is small, and the lower limit is preferably 0%. The content of Li ₂ O may be 0%.

In the optical glass of the first embodiment, the upper limit of the content of Na ₂ O is preferably 5%, and further preferably 4%, 3%, and 2% in this order. Preferably, the content of Na ₂ O is small, and the lower limit is preferably 0%. The content of Na ₂ O may be 0%.

In the optical glass of the first embodiment, the upper limit of the content of K ₂ O is preferably 5%, and further preferably 4%, 3%, and 2% in this order. Preferably, the content of K ₂ O is small, and the lower limit is preferably 0%. The content of K ₂ O may be 0%.

In the optical glass of the first 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 10%, and further preferably 5%, 4 %, 3%. The lower limit of the total content [Li ₂ O+Na ₂ O+K ₂ O] is preferably 0%.

Li ₂ O, Na ₂ O, and K ₂ O have the function of lowering the liquidus temperature and improving the thermal stability of the glass. However, when the content of these is too large, the chemical durability and weather resistance decrease. Therefore, each content of Li ₂ O, Na ₂ O, and K ₂ O and the total content of these are preferably within the above ranges.

In the optical glass of the first embodiment, the upper limit of the content of Cs ₂ O is preferably 5%, and further preferably 3%, 1%, and 0.5%. The lower limit of the content of Cs ₂ O is preferably 0%.

Cs ₂ O has the function of improving the thermal stability of glass, but when the content of these is too much, the chemical durability and weather resistance decrease. Therefore, the content of Cs ₂ O is preferably within the above range.

In the optical glass of the first embodiment, the upper limit of the content of MgO is preferably 5%, and further preferably 4%, 3%, and 2% in this order. Preferably, the content of MgO is small, and the lower limit is preferably 0%. The content of MgO may be 0%.

In the optical glass of the first embodiment, the upper limit of the content of CaO is preferably 5%, and further preferably 4%, 3%, and 2% in this order. Preferably, the content of CaO is small, and the lower limit is preferably 0%. The content of CaO may be 0%.

In the optical glass of the first embodiment, the upper limit of the content of SrO is preferably 5%, and further preferably 4%, 3%, and 2% in this order. Preferably, the content of SrO is small, and the lower limit is preferably 0%. The content of SrO may be 0%.

In the optical glass of the first embodiment, the upper limit of the content of BaO is preferably 5%, and further preferably 4%, 3%, and 2% in this order. Preferably, the content of BaO is small, and the lower limit is preferably 0%. The content of BaO may be 0%.

In the optical glass of the first embodiment, the upper limit of the total content [MgO+CaO+SrO+BaO] of MgO, CaO, SrO, and BaO is preferably 10%, and further preferably 5%, 4%, and 3% in order. In addition, the lower limit of the total content [MgO+CaO+SrO+BaO] is preferably 0%.

MgO, CaO, SrO, and BaO are glass components that have functions of improving thermal stability and resistance to devitrification. However, when the content of these glass components is excessive, the acid resistance, thermal stability, and devitrification resistance of the glass decrease. Therefore, the respective contents of MgO, CaO, SrO, and BaO and the total contents of these are preferably within the above ranges.

In the optical glass of the first embodiment, the upper limit of the content of ZnO is preferably 20%, and further preferably 15%, 10%, and 6% in this order. Preferably, the content of ZnO is small, and the lower limit is preferably 0%. The content of ZnO may be 0%. By setting the upper limit of the content of ZnO to the above range, the acid resistance and melting property of the glass can be improved.

In the optical glass of the first embodiment, the upper limit of the content of Gd ₂ O ₃ is preferably 20%, and further preferably 18%, 16%, and 15%. In addition, the lower limit of the content of Gd ₂ O ₃ is preferably 0%, and further preferably 1%, 2%, and 3% in this order. By setting the content of Gd ₂ O ₃ to the above range, it is possible to suppress an increase in raw material cost, and it is possible to achieve a desired optical constant.

In the optical glass of the first embodiment, the upper limit of the content of Y ₂ O ₃ is preferably 20%, and further preferably 18%, 15%, and 13%. In addition, the lower limit of the content of Y ₂ O ₃ is preferably 2%, and further preferably 4%, 5%, and 6% in this order. By setting the content of Y ₂ O ₃ to the above range, a desired optical constant can be achieved.

In the optical glass of the first embodiment, the upper limit of the content of ZrO ₂ is preferably 12%, and further preferably 10%, 9%, and 8%. In addition, the lower limit of the content of ZrO ₂ is preferably 0%, and further preferably 1%, 2%, and 3% in this order. The content of ZrO ₂ may be 0%. By setting the content of ZrO ₂ in the above range, the acid resistance of the glass can be improved, and the required optical constant can be achieved.

In the optical glass of the first embodiment, the upper limit of the content of TiO ₂ is preferably 10%, and further preferably 8%, 7%, and 6% in this order. In addition, the content of TiO ₂ is preferably small, and the lower limit is preferably 0%. The content of TiO ₂ may be 0%. By setting the content of TiO ₂ within the above range, the acid resistance of the glass can be improved, and the required optical constant can be achieved.

In the optical glass of the first embodiment, the upper limit of the content of Nb ₂ O ₅ is preferably 20%, and further preferably 15%, 12%, and 10% in this order. In addition, the lower limit of the content of Nb ₂ O ₅ is preferably 0%, and further preferably 1%, 2%, and 3% in this order. The content of Nb ₂ O ₅ may be 0%. By setting the content of Nb ₂ O ₅ to the above range, the acid resistance of the glass can be improved, and the required optical constant can be realized.

In the optical glass of the first embodiment, the upper limit of the content of WO ₃ is preferably 10%, and further preferably 8%, 7%, and 6%. Preferably, the content of WO ₃ is small, and the lower limit is preferably 0%. The content of WO ₃ may be 0%. By setting the content of WO ₃ to the above range, the acid resistance of the glass can be improved, and the required optical constant can be achieved.

In the optical glass of the first embodiment, the upper limit of the content of Bi ₂ O ₃ is preferably 10%, and further preferably 8%, 7%, and 6%. In addition, it is preferable that the content of Bi ₂ O ₃ is small, and the lower limit is preferably 0%. The content of Bi ₂ O ₃ may be 0%. By setting the content of Bi ₂ O ₃ to the above range, the corrosion of the molten container (Pt) is suppressed, and the desired optical constant can be realized.

In the optical glass of the first embodiment, the upper limit of the content of Ta ₂ O ₅ is preferably 20%, and further preferably 15%, 12%, and 10% in this order. In addition, the lower limit of the content of Ta ₂ O ₅ is preferably 0%, and further preferably 1%, 2%, and 3% in this order. The content of Ta ₂ O ₅ may be 0%. By setting the content of Ta ₂ O ₅ to the above range, the acid resistance of the glass can be improved, and the required optical constant can be achieved.

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%.

In the optical glass of the first 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%, and more preferably 0.05% and 0.1% in this order.

Sc ₂ O ₃ and HfO ₂ have the function of improving the high dispersion of glass, but they are expensive components. Therefore, it is preferable that the respective contents of Sc ₂ O ₃ and HfO ₂ fall within the above range.

In 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 function of improving the high dispersion of glass, but because of its large molecular weight, it is also a glass component that increases the specific gravity of glass. Therefore, the content of Lu ₂ O ₃ is preferably within the above range.

In the optical glass of the first 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%.

GeO ₂ has the function of improving the high dispersion of glass, but it is a particularly expensive component among the glass components generally used. Therefore, from the viewpoint of reducing the manufacturing cost of glass, the content of GeO ₂ is preferably in the above range.

In the optical glass of the first 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%.

When the content of Yb ₂ O ₃ is too large, the specific gravity of the glass increases, and the thermal stability of the glass may decrease. Therefore, the content of Yb ₂ O ₃ is preferably within the above range.

The optical glass of the first embodiment preferably consists mainly of the aforementioned glass components, namely B ₂ O ₃ , La ₂ O ₃ , Al ₂ O ₃ , SiO ₂ , P ₂ O ₅ , Li ₂ O, Na ₂ O, K ₂ O , Cs ₂ O, MgO, CaO, SrO, BaO, ZnO, Gd ₂ O ₃ , Y ₂ O ₃ , ZrO ₂ , TiO ₂ , Nb ₂ O ₅ , WO ₃ , Bi ₂ O ₃ , Ta ₂ O ₅ , Sc ₂ O ₃ , HfO ₂ , Lu ₂ O ₃ , GeO ₂ and Yb ₂ O ₃ , the total content of the above glass components is preferably more than 95%, more preferably more than 98%, and even more preferably more than 99%, More preferably, it is more than 99.5%.

In addition, the optical glass of the first embodiment is oxide glass, and the main component of the anion component is O (oxygen). The upper limit of the content of the added F (fluorine) with respect to the total mass of the oxide standard is preferably 2%, and further preferably 1.5%, 1%, and 0.5%. Preferably, the content of F is small, and it may be 0%. When the content of F is excessive, the glass component easily volatilizes when the glass is melted, and the composition of the molten glass may be unstable.

In the present invention and the present specification, the content of F (fluorine) is assuming that the glass is composed of an oxide in which all cationic components constituting the glass are combined with charge-matched oxygen, and the glass composed of these oxides as a whole The mass of is set to 100%, and the mass of F is expressed by mass% (plus mass% for the mass of the oxide standard).

In addition, the optical glass of the present embodiment is preferably composed of the above-mentioned glass components in principle, but can also contain other components within a range that does not hinder the operational effects of the present invention. In addition, in the present invention, the inclusion of unavoidable impurities is not excluded.

(Other ingredients)

In addition to the above-mentioned components, the above-mentioned optical glass can also contain a small amount of Sb ₂ O ₃ , CeO ₂ and the like as a clarifying agent. The total amount (additional addition amount) of the clarifying agent is 0% or more, preferably less than 1%, more preferably 0% or more and 0.5% or less.

The added amount refers to the added amount of the clarifying agent expressed in mass% when the total content of all glass components except the clarifying agent is 100%.

Pb, Cd, As, Th, etc. are components that may cause a burden on the environment. Therefore, the content of each of PbO, CdO, As ₂ O ₃ , and ThO ₂ is preferably 0 to 0.1%, more preferably 0 to 0.05%, and still more preferably 0 to 0.01%. It is particularly preferred that PbO, CdO, As ₂ O ₃ and ThO _{2 are} not substantially included.

Furthermore, the above-mentioned optical glass can obtain high transmittance in a wide range of the entire visible light region. In order to effectively utilize such characteristics, it is preferable that the optical glass does not contain coloring elements. As coloring elements, Cu, Co, Ni, Fe, Cr, Eu, Nd, Er, V, etc. can be exemplified. Any element is preferably less than 100 mass ppm, more preferably 0 to 80 mass ppm, still more preferably 0 to 50 mass ppm, and particularly preferably not substantially included.

In addition, Ga, Te, Tb, etc. are components that are not necessarily introduced, and are also expensive components. Therefore, the range of the contents of Ga ₂ O ₃ , TeO ₂ , and TbO ₂ expressed in mass% is preferably 0 to 0.1%, more preferably 0 to 0.05%, further preferably 0 to 0.01%, and further It is preferably 0 to 0.005%, still more preferably 0 to 0.001%, and particularly preferably not substantially included.

(Glass characteristics)

>Specific gravity of glass>

The specific gravity of the optical glass of the first embodiment is preferably 5.00 or less, and further preferably 4.90 or less, 4.80 or less, and 4.70 or less in this order. The smaller the specific gravity, the better. The lower limit is not particularly limited, but is usually about 4.00. The components that relatively increase the specific gravity are BaO, La ₂ O ₃ , ZrO ₂ , Nb ₂ O ₅ , Ta ₂ O ₅ and the like. The components that relatively reduce the specific gravity are SiO ₂ , B ₂ O ₃ , Li ₂ O, Na ₂ O, K ₂ O, and the like. By adjusting the content of these ingredients, the specific gravity can be controlled.

>Light transmittance of glass>

The light transmittance of the optical glass of the first embodiment can be evaluated by the coloring degrees λ80, λ70, and λ5.

For a glass test sample with a thickness of 10.0 mm ± 0.1 mm, the spectral transmittance was measured in the range of 200 to 700 nm, the wavelength with an external transmittance of 80% was λ80, and the wavelength with an external transmittance of 70% was λ70 The wavelength at which the external transmittance is 5% is λ5.

The λ80 of the optical glass of the first embodiment is preferably 500 nm or less, more preferably 470 nm or less, and still more preferably 450 nm or less.

In addition, λ70 is preferably 400 nm or less, more preferably 395 nm or less, and still more preferably 390 nm or less.

λ5 is preferably 350 nm or less, more preferably 345 nm or less, and still more preferably 340 nm or less.

(Manufacture of optical glass)

With regard to the optical glass of the first embodiment, the glass raw material is prepared to the above-mentioned predetermined composition, and the prepared glass raw material may be prepared according to a known glass production method. For example, a plurality of compounds are blended and mixed sufficiently to make a batch of raw materials, and the batch of raw materials is put into a quartz crucible and a platinum crucible to perform rough melting. The molten material obtained by rough melting was quenched and pulverized, and then the broken glass was produced. Furthermore, the broken glass was put into a platinum crucible, heated, and remelted (mellt) to make molten glass. After being clarified and homogenized, the molten glass was molded and slowly cooled to obtain optical glass. Known methods can be applied to the molding and slow cooling of molten glass.

In addition, if the required glass component can be introduced into the glass to a desired content, the compound used when preparing the batch of raw materials is not particularly limited, and the following compounds may be mentioned: oxides, carbonates, nitrates, hydrogen Oxides, fluorides, etc.

(Manufacture of optical elements, etc.)

When manufacturing the optical element using the optical glass of the first embodiment, a known method can be applied. For example, in the production of the above-mentioned optical glass, molten glass is poured into a mold and formed into a plate shape to produce a glass element composed of the optical glass of the present invention. The obtained glass element is appropriately cut, polished, and polished to produce a cut piece of a size and shape suitable for press molding. The cut piece is heated and softened, and reheat press is performed using a known method to produce an optical element blank similar to the shape of the optical element. The optical element blank is annealed, and is ground and polished using a known method to produce an optical element.

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

According to one 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 lenses such as spherical lenses and aspheric lenses, prisms, and diffraction gratings. As the shape of the lens, various shapes such as a lenticular lens, a plano-convex lens, a biconcave lens, a plano-concave lens, a convex lenticular lens, a concave lenticular lens and the like can be exemplified. 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. Examples of processing include cutting, grinding, rough grinding, fine grinding, and polishing. When such processing is performed, damage can be reduced by using the above-mentioned glass, and a high-quality optical element can be stably supplied.

Second embodiment

The optical glass of the second embodiment of the present invention has a refractive index nd of 1.70 to 1.85, an Abbe number νd of 42 to 55, a content of SiO ₂ of 5 to 20%, and a content of B ₂ O ₃ of 5 to 35% , The content of La ₂ O ₃ is 25-50%, the content of Al ₂ O ₃ is 1-20%, the mass ratio of the content of B ₂ O _{3 to} the content of Al ₂ O ₃ [B ₂ O ₃ /Al ₂ O ₃ ] is 8 or less, and the optical glass is characterized in that the content of F is applied and is 2% or less.

Hereinafter, the optical glass of the second embodiment will be described in detail.

In the optical glass of the second embodiment, the refractive index nd is 1.70 to 1.85. The refractive index nd can also be set to 1.71 to 1.84, or 1.72 to 1.83.

In the optical glass of the second embodiment, the Abbe number νd is 42 to 55. The Abbe number νd can also be set to 43 to 54.5, or 44 to 54.

In the optical glass of the second embodiment, the content of SiO ₂ is 5 to 20%. The upper limit of the content of SiO ₂ is preferably 17%, and further preferably 14% and 12%. In addition, the lower limit of the content of SiO ₂ is preferably 6%, and further preferably 7% and 8%.

When the content of SiO ₂ is too large, the acid resistance, devitrification resistance, and chemical durability may decrease. In addition, when the content of SiO ₂ is too small, slag of the glass raw material is likely to be generated when the glass is melted.

In the optical glass of the second embodiment, the content of B ₂ O ₃ is 5 to 35%. The upper limit of the content of B ₂ O ₃ is preferably 31%, and further preferably 29%, 27%, and 25%. In addition, the lower limit of the content of B ₂ O ₃ is preferably 7%, and further preferably 8%, 9%, and 10% in order.

When the content of B ₂ O ₃ is too large, the acid resistance may decrease. In addition, when the content of B ₂ O ₃ is too small, the thermal stability of the glass may decrease.

In the optical glass of the second embodiment, the content of La ₂ O ₃ is 25 to 50%. The upper limit of the content of La ₂ O ₃ is preferably 48%, and further preferably 46%, 44%, and 42%. In addition, the lower limit of the content of La ₂ O ₃ is preferably 27%, and further preferably 28%, 29%, and 30% in this order.

By setting the content of La ₂ O ₃ to the above range, the acid resistance of the glass can be improved, and the required optical constant can be achieved.

In the optical glass of the second embodiment, the content of Al ₂ O ₃ is 1 to 20%. The upper limit of the content of Al ₂ O ₃ is preferably 18%, and further preferably 16%, 15%, and 14%. In addition, the lower limit of the content of Al ₂ O ₃ is preferably 2%, and further preferably 3%, 4%, and 5% in this order.

When the content of Al ₂ O ₃ is too large, the liquidus temperature LT may increase, and it becomes highly dispersive, and an optical glass having a desired optical constant cannot be obtained. In addition, when the content of Al ₂ O ₃ is too small, the acid resistance may decrease.

In the optical glass of the second embodiment, the content of B ₂ O ₃ with respect to the mass content of Al ₂ O ₃ ratio [B ₂ O ₃ / Al ₂ O _3] is 8 or less. The upper limit of the mass ratio [B ₂ O ₃ /Al ₂ O ₃ ] is preferably 5, and further preferably 4, 3 in order. In addition, the lower limit of the mass ratio [B ₂ O ₃ /Al ₂ O ₃ ] is preferably 0.5, and further preferably 0.6, 0.7, and 0.8 in this order.

When the mass ratio [B ₂ O ₃ /Al ₂ O ₃ ] is too large, the acid resistance may decrease. In addition, when the mass ratio [B ₂ O ₃ /Al ₂ O ₃ ] is too small, it may not be possible to obtain an optical glass having a desired optical constant.

The optical glass of the second embodiment is oxide glass, and the main component of the anion component is O (oxygen). Moreover, the upper limit of the content of the added F (fluorine) with respect to the total mass of the oxide standard is 2%. The upper limit of the content of F (fluorine) is preferably 1.5%, and further preferably 1% and 0.5% in order. The smaller the content of F, the better. It may be 0%. When the content of F is excessive, the glass component easily volatilizes when the glass is melted, and the composition of the glass may be unstable.

The content and ratio of glass components other than the above in the optical glass of the second embodiment can be the same as those of the first embodiment.

(Glass characteristics)

>Acid resistance>

In the optical glass of the second embodiment, when the Abbe number νd is 42 or more and less than 50, the acid resistance based on JOGIS is preferably grade 1 to grade 2, and more preferably grade 1. In addition, when the Abbe number νd is 50 or more and 55 or less, the acid resistance based on JOGIS is preferably 1 to 3 grades, more preferably 1 to 2 grades, and still more preferably 1 grade. The acid resistance evaluation based on JOGIS can be performed in the same manner as in the first embodiment.

The specific gravity of the optical glass of the second embodiment and the light transmittance of the glass can be the same as those of the first embodiment.

In addition, the manufacturing of the optical glass and the manufacturing of the optical element and the like in the second embodiment can also be made the same as in the first embodiment.

[Example]

Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples.

(Example 1)

A glass sample having the glass composition shown in Table 2 was prepared according to the following procedure, and various evaluations were performed.

[Manufacture of optical glass]

First, prepare oxides, hydroxides, carbonates, and nitrates corresponding to the constituent components of the glass as raw materials, and weigh and mix the raw materials so that the glass composition of the obtained optical glass becomes each composition shown in Table 2. , Fully mix the raw materials. The prepared raw material (batch raw material) thus obtained is put into a platinum crucible, heated at 1200°C to 1450°C for 2 to 5 hours to make molten glass, stirred and homogenized, and clarified, after which the molten glass is cast into preheating To a suitable temperature in a metal mold. The cast glass is heat-treated for 30 to 120 minutes at any temperature between the temperature lower than the glass transition temperature Tg by 100°C (Tg-100°C) and the temperature higher than Tg by 30°C (Tg+30°C). The inside was cooled to room temperature, thereby obtaining a glass sample.

[Confirmation of glass composition]

With respect to the obtained glass sample, the content of each glass component was measured by inductively coupled plasma atomic emission spectrometry (ICP-AES), and the composition shown in Table 2 was confirmed.

[Measurement of acid resistance weight loss rate Da]

According to the provisions of the Japanese Optical Glass Industry Standard JOGIS06-2009, the obtained glass samples were made into powder glass (particle size 425-600 μm) with a weight corresponding to specific gravity, and placed in a platinum cage, which was immersed in containing 0.01mol/L nitric acid The aqueous solution in the quartz glass round bottom flask was treated in a boiling water bath for 60 minutes, and the weight reduction rate (%) before and after the treatment was measured. In addition, this weight reduction rate was evaluated in grades. The results are shown in Table 3.

[Measurement of optical properties]

After the obtained glass sample was further annealed for about 30 minutes to about 2 hours near the glass transition temperature Tg, it was cooled to room temperature at a temperature reduction rate of -30°C/hour in the furnace to obtain an annealed sample. The refractive index nd, Abbe number νd, specific gravity, λ80, λ70 and λ5 were measured for the obtained annealed sample. The results are shown in Table 3.

(i) Refractive index nd and Abbe number νd

For the above-mentioned annealed samples, the refractive indexes nd, ng, nF, and nC were measured by the refractive index measurement method of JIS standard JISB7071-1, and the Abbe number νd was calculated based on the following formula. νd=(nd-1)/(nF-nC)

(ii) Specific gravity

The specific gravity is determined by the Archimedes method.

(iii) λ80, λ70, λ5

The above-mentioned annealed samples were processed into planes with a thickness of 10 mm, having mutually parallel and optically polished surfaces, and the spectral transmittance in the wavelength range from 280 nm to 700 nm was measured. Let the intensity of the light incident perpendicularly to the plane on the side of the optical polishing be intensity A, and let the intensity of the light emitted from the other surface be the intensity B, and calculate the spectral transmittance B/A. The wavelength with a spectral transmittance of 80% is λ80, the wavelength with a spectral transmittance of 70% is λ70, and the wavelength with a spectral transmittance of 5% is λ5. In addition, the spectral transmittance also includes the reflection loss of light on the sample surface.

[Table 2]

[table 3]

(Example 2)

Using the glass sample obtained in Example 1, a preform for precision press molding was produced by a known method. The obtained preform is heated and softened in a nitrogen environment, and precision press-molded by a press-molding mold to shape the optical glass into the shape of an aspheric lens. After that, the molded optical glass is taken out from the press mold, and an aspheric lens is obtained by annealing and coring.

(Example 3)

The glass sample obtained in Example 1 was cut and polished to produce cut pieces. The optical element blank is made by reheating and pressing to press the cut pieces. Precise annealing of the optical element blanks, after accurately adjusting the refractive index to the desired refractive index, by grinding and polishing using known methods, obtain biconvex lenses, biconcave lenses, plano-convex lenses, plano-concave lenses, concave mirror properties Various lenses such as meniscus lenses and convex mirror-type meniscus lenses.

It should be considered that the embodiment disclosed this time is an example in all respects and not a limitation. The scope of the present invention is shown by the scope of the patent claim rather than the above description, and is intended to include the meaning equivalent to the scope of the patent claim and all changes within the scope.

For example, regarding the glass composition exemplified above, the optical glass according to one embodiment of the present invention can be produced by adjusting the composition described in the specification.

In addition, it is obvious that two or more items exemplified in the specification or described in a preferred range can be arbitrarily combined.

no.

no.

Claims (4)

An optical glass with a refractive index nd of 1.70 to 1.85, a B ₂ O ₃ content of 5 to 35% by mass, a La ₂ O ₃ content of 25 to 50% by mass, and an Al ₂ O ₃ content of 1 to 20% by mass , And the optical glass satisfies the following (a) or (b), (a): Abbe number νd is 42 or more and less than 50, based on JOGIS acid resistance is 1 to 2, (b): Abbe number νd It is 50 or more and 55 or less, and the acid resistance based on JOGIS is 1 to 3 grades. An optical glass with a refractive index nd of 1.70 to 1.85, an Abbe number νd of 42 to 55, a content of SiO ₂ of 5 to 20% by mass, a content of B ₂ O ₃ of 5 to 35% by mass, and a La ₂ O ₃ The content is 25-50% by mass, the content of Al ₂ O ₃ is 1-20% by mass, and the mass ratio of the content of B ₂ O _{3 to} the content of Al ₂ O ₃ [B ₂ O ₃ /Al ₂ O ₃ ] is 8 or less, and the content of F is added, and is 2% by mass or less. An optical element blank composed of optical glass as described in item 1 or 2 of the patent application. An optical element is composed of the optical element blank as described in item 3 of the patent application scope.