CN105985017B

CN105985017B - Optical glass and optical element

Info

Publication number: CN105985017B
Application number: CN201610128993.XA
Authority: CN
Inventors: 武藤秀树; 藤原康裕
Original assignee: Hoya Corp
Current assignee: Hoya Corp
Priority date: 2015-03-17
Filing date: 2016-03-07
Publication date: 2018-11-30
Anticipated expiration: 2036-03-07
Also published as: JP2016172670A; TW201634416A; CN105985017A; TWI706924B; TWI771744B; JP6576657B2; TW202104113A

Abstract

The present invention provide it is a kind of can reduce the production costs such as raw material expense, meltbility and thermal stability it is outstanding and also with softening temperature high-refractivity and low-dispersion optical glass.The optical element and optical glass material that the present invention also provides a kind of to be made of such optical glass.A kind of optical glass, wherein it relative to the ratio [HR1/RE1] of RE1 is 0.33 hereinafter, Nb that RE1, which is 0.35 or more, HR1 relative to the ratio [RE1/NWF1] of NWF1,₂O₅Content relative to Nb₂O₅And Ta₂O₅Total content mass ratio [Nb₂O₅/(Nb₂O₅+Ta₂O₅)] it is 2/3 or more, RE1 is 0.90 or more relative to the ratio [RE1/D1] of D1, L1 is 0.78 or more relative to the ratio [L1/ (NWF1+RE1)] of the aggregate value of NWF1 and RE1, Abbe number ν d is 39.0 or more, 45.0 or less, above-mentioned Abbe number ν d and refractive index nd meet following (1) formulas, nd >=2.235-0.01 × ν d (1).

Description

Optical glass and optical element

Technical Field

The present invention relates to an optical glass having a high refractive index and low dispersion, which can be produced at a low cost and has excellent meltability and thermal stability. The invention also relates to an optical element made of such an optical glass.

Background

Generally, an optical glass having a high refractive index and low dispersion contains a rare earth oxide such as boron oxide and lanthanum oxide. In such an optical glass, in order to increase the refractive index without reducing the abbe number, it is necessary to increase the content of the rare earth oxide. However, when the content of the rare earth oxide is increased in such an optical glass, the thermal stability of the glass is lowered, and the glass is crystallized during the glass production process, so that it is difficult to obtain a transparent glass (the glass is devitrified). Therefore, when the refractive index is increased without decreasing the abbe number, it becomes difficult to manufacture the optical glass.

On the other hand, optical glasses having a high refractive index and a large abbe number have high utility values in designing optical systems, for correcting chromatic aberration, and for making optical systems highly functional and compact.

Among glasses having high refractive index and low dispersion characteristics, a glass suitable for precision press molding has a large amount of Zn or Li introduced therein, which has an action of softening the glass at a low temperature. Such glasses are described in patent documents 1 to 7.

A high-refractive-index low-dispersion glass, particularly a glass having optical characteristics in a range where (abbe number ν d, refractive index nd) is 2 points connected between a (45, 1.785) and B (40, 1.835) in an optical characteristic diagram (also referred to as an abbe diagram) and the refractive index nd is higher than that of the straight line C, is highly valuable in optical design.

On the other hand, as described in patent documents 1, 2, and 6, in order to lower the glass transition temperature Tg while maintaining thermal stability, it is necessary to introduce a large amount of tantalum oxide into such a glass. However, tantalum oxide is rare and valuable, and it is not easy to stably supply it as a glass raw material. Further, tantalum oxide is extremely expensive, and this causes the price of glass to increase.

On the other hand, patent documents 3 to 5 and 7 disclose glasses in which the content of Ta is reduced, but the refractive index is lower than the straight line C, and the requirements in terms of optical design are not satisfied.

Further, improvement of the meltability of the optical glass is required. By improving the meltability of the glass, satisfactory improvement effects can be expected for transmittance and refining performance. The details are as follows.

First, the effect of improving meltability on transmittance will be described.

In general, in the case of glass having poor meltability, there is a problem that a glass raw material remains melted in the glass. Such a molten residue of the glass raw material causes a change in glass composition and deterioration in homogeneity of the glass. Therefore, the glass is usually produced by increasing the melting temperature and the melting time so that the glass raw material does not remain melted.

However, although the problem of the residual molten glass material can be solved by increasing the melting temperature and the melting time, it causes new problems such as deterioration of the melting vessel and increase of the production cost. In particular, erosion of the melting vessel by the molten glass is a big problem.

In general, when melting glass that requires high homogeneity, such as optical glass, a crucible made of a noble metal, such as a platinum crucible, is widely used as a melting vessel. A crucible made of a noble metal is less susceptible to erosion by molten glass than a crucible made of another material. However, when glass having poor meltability is melted as described above, since high-temperature molten glass is in contact with the crucible for a long time, even a crucible made of a noble metal is corroded by the molten glass.

For example, in the case of a platinum crucible, platinum constituting the crucible may be mixed as a solid into molten glass due to erosion of the molten glass. Such a solid becomes an impurity in the glass and becomes a scattering source of light. Further, when the crucible is slightly eroded to dissolve platinum as ions into the molten glass, coloration of the optical glass as a product is enhanced due to light absorption by the platinum ions dissolved into the glass, and transmittance in the visible light region is lowered.

On the other hand, if the glass is a glass having excellent meltability, the problem of residual molten glass raw materials is less likely to occur. Therefore, it is not necessary to increase the melting temperature or extend the melting time, and erosion of the molten glass to the melting vessel can be suppressed. Further, the lowering of the transmittance of the glass due to the increase in the melting temperature and the extension of the melting time can be suppressed.

That is, by improving the meltability, the homogeneity of the glass can be improved and the decrease in the transmittance in the visible light region can be suppressed.

Next, the effect of improving the meltability on the clarity will be described.

In general, in a method (crude melting-remelting system) for producing optical glass by roughly melting (rough melt) batch raw materials (raw materials in which a plurality of compounds are blended) to produce cullet raw materials and remelting (remelt) the cullet raw materials, when defoaming (that is, improving fining (defoaming)) of remelted molten glass is improved, it is preferable that a large amount of gas components contained in the cullet are dissolved in the molten glass before fining, that is, the amount of gas components dissolved in the molten glass before fining is increased.

Here, the gas components include, for example, water vapor and CO generated by heating and decomposing boric acid, carbonate, nitrate, sulfate, hydroxide, and the like contained in the batch raw material_x、NO_xAnd SO_xAnd the like.

As described above, when producing glass having poor meltability, it is necessary to increase the melting temperature and extend the melting time so as not to cause a residual molten glass material. In particular, gases derived from the raw materials are easily released from the melt of the batch raw materials at high temperatures, and if the time for coarse melting becomes longer, sufficient gas components do not remain in the cullet.

Generally, when cullet is remelted, gas components remaining in the cullet become bubbles in the molten glass, and form large bubbles together with fine bubbles. The bubbles in the molten glass are larger than the fine bubbles in the molten glass in the floating speed, and can quickly reach the liquid surface of the molten glass and be discharged to the outside of the molten glass. Therefore, the molten glass can be refined in a short time. However, in the case of glass having poor melting properties as described above, since a sufficient amount of gas component does not remain in the cullet, it is difficult to grow fine bubbles into large bubbles, and it is difficult to discharge the fine bubbles out of the molten glass. Therefore, the optical glass cannot be sufficiently clarified, and thus has a problem that fine bubbles remain in the optical glass as a product.

On the other hand, in the rough melting of glass having excellent meltability, the batch raw materials can be melted at a relatively low temperature. Therefore, cullet can be produced in a state where a large amount of gas components are dissolved in the melt. As a result, the molten glass can be refined in a short time by using the cullets.

That is, by improving the meltability, the fining property of the glass can be improved, and the amount of glass produced per unit time can be increased.

As described above, by improving the meltability, not only the transmittance of the glass but also the fining property can be improved. Further, by improving the meltability, energy consumed for melting glass can be reduced, and the melting time can be shortened, so that reduction in production cost and improvement in productivity can be expected. Thus, it can be said that it is very advantageous to improve the meltability.

Documents of the prior art

Patent document

Patent document 1: U.S. patent No. 7897533;

patent document 2: japanese patent laid-open No. 2003-201142;

patent document 3: japanese Kokai publication 2002-012443;

patent document 4: japanese Kokai publication 2009-537427;

patent document 5: japanese patent laid-open No. 2003-201142;

patent document 6: japanese Kokai publication No. 2009-203083;

patent document 7: japanese Kokai publication 2009-537427.

Disclosure of Invention

Problems to be solved by the invention

The present invention has been made in view of such circumstances, and an object thereof is to provide an optical glass having a high refractive index and low dispersion, which is excellent in meltability and thermal stability and has a low-temperature softening property, and which can be produced at a low cost such as a raw material cost. It is another object of the present invention to provide an optical element and an optical glass material each comprising the above optical glass.

Means for solving the problems

The present inventors have made extensive studies to achieve the above object, and as a result, have found that the object can be achieved by reducing the amount of tantalum oxide, which is a relatively expensive material, and adjusting the balance of the content ratios of various glass components (hereinafter referred to as glass components) constituting the glass, and have completed the present invention based on this knowledge.

That is, the gist of the present invention is as follows.

(1) An optical glass, wherein,

the ratio [ RE1/NWF1] of RE1 to NWF1 is 0.35 or more,

the ratio [ HR1/RE1] of HR1 to RE1 is 0.33 or less,

Nb₂O₅relative to the content of Nb₂O₅And Ta₂O₅The mass ratio of the total content of [ Nb ]₂O₅/(Nb₂O₅+Ta₂O₅)]The content of the amino acid is above 2/3,

the ratio [ RE1/D1] of RE1 to D1 is 0.90 or more,

the ratio [ L1/(NWF1+ RE1) ] of L1 to the total value of NWF1 and RE1 is 0.78 or more,

abbe number vd is 39.0-45.0, and the Abbe number vd and refractive index nd satisfy the following formula (1),

nd≥2.235-0.01×νd···(1)

wherein,

when mixing M (B)₂O₃)、M(SiO₂)、M(Al₂O₃)、M(La₂O₃)、M(Gd₂O₃)、M(Y₂O₃)、M(Yb₂O₃)、M(LaF₃)、M(GdF₃)、M(YF₃)、M(YbF₃)、M(ZnO)、M(Li₂O)、M(Na₂O)、M(K₂O)、M(ZrO₂)、M(Nb₂O₅)、M(TiO₂)、M(WO₃)、M(Ta₂O₅)、M(Bi₂O₃)、M(MgO)、M(CaO, M (SrO), M (BaO) are B₂O₃、SiO₂、Al₂O₃、La₂O₃、Gd₂O₃、Y₂O₃、Yb₂O₃、LaF₃、GdF₃、YF₃、YbF₃、ZnO、Li₂O、Na₂O、K₂O、ZrO₂、Nb₂O₅、TiO₂、WO₃、Ta₂O₅、Bi₂O₃MgO, CaO, SrO and BaO,

NWF1＝[2×B₂O₃/M(B₂O₃)]+[SiO₂/M(SiO₂)]+[2×Al₂O₃/M(Al₂O₃)]

RE1＝[2×La₂O₃/M(La₂O₃)]+[2×Gd₂O₃/M(Gd₂O₃)]+[2×Y₂O₃/M(Y₂O₃)]+[2×Yb₂O₃/M(Yb₂O₃)]+[LaF₃/M(LaF₃)]+[GdF₃/M(GdF₃)]+[YF₃/M(YF₃)]+[YbF₃/M(YbF₃)]

HR1＝[2×Nb₂O₅/M(Nb₂O₅)]+[TiO₂/M(TiO₂)]+[WO₃/M(WO₃)]+[2×Bi₂O₃/M(Bi₂O₃)]

D1＝{[2×Li₂O/M(Li₂O)]+[2×Na₂O/M(Na₂O)]+[2×K₂O/M(K₂O)]}×3+[ZnO/M(ZnO)]

L1＝[20×Li₂O/M(Li₂O)]+[16×Na₂O/M(Na₂O)]+[8×K₂O/M(K₂O)]+[4×ZnO/M(ZnO)]+[MgO/M(MgO)]+[2×CaO/M(CaO)]+[2×SrO/M(SrO)]+[2×BaO/M(BaO)]+[2×B₂O₃/M(B₂O₃)]+[2×Nb₂O₅/M(Nb₂O₅)]+[TiO₂/M(TiO₂)]+[4×WO₃/M(WO₃)]+[8×Bi₂O₃/M(Bi₂O₃)]+[2×Ta₂O₅/M(Ta₂O₅)]-[2×SiO₂/M(SiO₂)]-[2×Al₂O₃/M(Al₂O₃)]-[2×ZrO₂/M(ZrO₂)]-[2×La₂O₃/M(La₂O₃)]-[2×Gd₂O₃/M(Gd₂O₃)]-[2×Y₂O₃/M(Y₂O₃)]-[2×Yb₂O₃/M(Yb₂O₃)]-[LaF₃/M(LaF₃)]-[GdF₃/M(GdF₃)]-[YF₃/M(YF₃)]-[YbF₃/M(YbF₃)]，

the content of each glass component is a value expressed by mass%.

(2) An optical glass which is an oxide glass, wherein,

the ratio [ RE2/NWF2] of RE2 to NWF2 is 0.35 or more,

the ratio [ HR2/RE2] of HR2 to RE2 is 0.33 or less,

Nb⁵⁺relative to the content of Nb⁵⁺And Ta⁵⁺Cation ratio of the total content of [ Nb ]⁵⁺/(Nb⁵⁺+Ta⁵⁺)]The content of the amino acid is above 3/4,

the ratio [ RE2/D2] of RE2 to D2 is 0.90 or more,

the ratio [ L2/(NWF2+ RE2) ] of L2 to the total value of NWF2 and RE2 is 0.78 or more,

abbe number vd is 39.0 or more and 45.0 or less, and the Abbe number vd and the refractive index nd satisfy the following formula (1):

nd≥2.235-0.01×νd···(1)

wherein,

NWF2 is B³⁺、Si⁴⁺And Al³⁺The total content of (a) to (b),

RE2 is La³⁺、Gd³⁺、Y³⁺And Yb³⁺The total content of (a) to (b),

HR2 is Nb⁵⁺、Ti⁴⁺、W⁶⁺And Bi³⁺The total content of (a) to (b),

D2＝(Li⁺+Na⁺+K⁺)×6+Zn²⁺，

L2＝(10×Li⁺)+(8×Na⁺)+(4×K⁺)+(4×Zn⁺)+Mg²⁺+(2×Ca²⁺)+(2×Sr²⁺)+(2×Ba² ⁺)+B³⁺+Nb⁵⁺+Ti⁴⁺+(4×W⁶⁺)+(4×Bi³⁺)+Ta⁵⁺-(2×Si⁴⁺)-Al³⁺-(2×Zr⁴⁺)-La³⁺-Gd³⁺-Y³⁺-Yb³⁺，

the content of each glass component is a value expressed as cation%.

(3) A preform for precision press molding, which comprises the optical glass according to the above (1) or (2).

(4) An optical element comprising the optical glass according to the above (1) or (2).

Effects of the invention

According to the present invention, it is possible to provide an optical glass having a high refractive index and low dispersion which can be produced at a low cost and is excellent in meltability and thermal stability and has softening properties at a low temperature, and an optical element using the optical glass.

Drawings

Fig. 1 is a graph in which the horizontal axis represents the ratio of L1 to the total value of NWF1 and RE1 [ L1/(NWF1+ RE1) ] and the vertical axis represents the glass transition temperature Tg of a known glass.

Fig. 2 is a graph in which the horizontal axis represents the ratio of L2 to the total value of NWF2 and RE2 [ L2/(NWF2+ RE2) ] and the vertical axis represents the glass transition temperature Tg of a known glass.

Detailed Description

Hereinafter, a mode for carrying out the present invention (hereinafter, simply referred to as "embodiment") will be described in detail. The following embodiments are illustrative of the present invention, and the present invention is not limited to the following embodiments. The present invention can be suitably modified and implemented within the scope of the gist thereof. Further, although description of overlapping portions may be appropriately omitted, the description is not intended to limit the spirit of the present invention. In the present specification, the term "optical glass" refers to a glass composition containing a plurality of glass components (glass components), and is used as a generic term regardless of shape (bulk, plate, sphere, etc.), use (material for optical element, etc.), and size. That is, there is no limitation on the shape, use and size of the optical glass, and any shape of optical glass, any use of optical glass and any size of optical glass belong to the optical glass of the present invention. In the present specification, the optical glass may be simply referred to as "glass".

In the present specification, the numerical range may be expressed by the expression "(numerical value 1) or less" (numerical value 1). The range thus represented is a numerical range smaller than (value 1) plus (value 1). The numerical range represented by "less than (numerical value 1)" is a numerical range smaller than (numerical value 1), and does not include (numerical value 1). The numerical range may be expressed by "(numerical value 2) or more" using (numerical value 2). The range thus expressed is a numerical range greater than (number 2) plus (number 2). Numerical ranges are sometimes expressed as "exceeding (value 2)". The range thus represented is a numerical range larger than (numerical value 2), and does not include (numerical value 2).

First, a glass composition expressed by mass% will be described as embodiment 1, and next, a glass composition expressed by cation% will be described as embodiment 2.

Embodiment 1

(composition in% by mass)

Hereinafter, the glass composition is expressed in terms of oxides.

The optical glass according to embodiment 1 of the present invention is an optical glass in which,

the ratio [ RE1/NWF1] of RE1 to NWF1 is 0.35 or more,

the ratio [ HR1/RE1] of HR1 to RE1 is 0.33 or less,

the ratio [ RE1/D1] of RE1 to D1 is 0.90 or more,

nd≥2.235-0.01×νd···(1)

wherein,

when mixing M (B)₂O₃)、M(SiO₂)、M(Al₂O₃)、M(La₂O₃)、M(Gd₂O₃)、M(Y₂O₃)、M(Yb₂O₃)、M(LaF₃)、M(GdF₃)、M(YF₃)、M(YbF₃)、M(ZnO)、M(Li₂O)、M(Na₂O)、M(K₂O)、M(ZrO₂)、M(Nb₂O₅)、M(TiO₂)、M(WO₃)、M(Ta₂O₅)、M(Bi₂O₃) M (MgO), M (CaO), M (SrO), M (BaO) are B₂O₃、SiO₂、Al₂O₃、La₂O₃、Gd₂O₃、Y₂O₃、Yb₂O₃、LaF₃、GdF₃、YF₃、YbF₃、ZnO、Li₂O、Na₂O、K₂O、ZrO₂、Nb₂O₅、TiO₂、WO₃、Ta₂O₅、Bi₂O₃MgO, CaO, SrO and BaO,

NWF1＝[2×B₂O₃/M(B₂O₃)]+[SiO₂/M(SiO₂)]+[2×Al₂O₃/M(Al₂O₃)]

the content of each glass component is a value expressed by mass%.

In the above formula, B represents₂O₃、SiO₂、Al₂O₃、La₂O₃、Gd₂O₃、Y₂O₃、Yb₂O₃、Nb₂O₅、TiO₂、WO₃、Bi₂O₃、Li₂O、Na₂O、K₂O、ZnO、MgO、CaO、SrO、BaO、Ta₂O₅、ZrO₂、LaF₃、GdF₃、YF₃And YbF₃The content of each glass component (2) is a content ratio of each glass component expressed by mass%. Symbols representing percentages such as NWF1, RE1, HR1, L1, and D1 are not added by mass% or% and are represented by numerical values. The same applies to the following description.

In the present embodiment, the optical glass of the present invention will be described based on the content of each glass component expressed by mass%. Therefore, unless otherwise specified below, the respective contents are expressed in mass%.

In the present specification, the term "mass%" means the content of each glass component represented by an oxide or a fluoride, wherein the total content of all the glass components is 100 mass% as represented by mass percentage.

As described later, a small amount of Sb may be added to the glass₂O₃、SnO₂、CeO₂As a clarifying agent. However, in the present specification, Sb is not included in the total content of all glass components in terms of mass%₂O₃、SnO₂And CeO₂The content of (a). Namely, Sb in the glass component₂O₃、SnO₂、CeO₂The respective contents of (A) and (B) are expressed as Sb₂O₃、SnO₂And CeO₂Sb content of all glass components except for 100 mass%₂O₃、SnO₂、CeO₂In each case. Such a representation is referred to as an add-on in this specification.

The total content is a total amount of the contents of the plurality of glass components (including a case where the content is 0%). The mass ratio is a ratio of contents of glass components (including a total content of a plurality of components) expressed by mass% to each other.

B is as follows₂O₃Molecular weight of (A) is M (B)₂O₃) Mixing SiO₂Molecular weight of (2) is set to M (SiO)₂) Mixing Al₂O₃Molecular weight of (2) is M (Al)₂O₃) Adding La₂O₃Molecular weight of (2) is M (La)₂O₃) Gd is added₂O₃Molecular weight of (2) is M (Gd)₂O₃) Is a reaction of Y₂O₃Molecular weight of (2) is M (Y)₂O₃) Is formed of Yb₂O₃Molecular weight of (2) is M (Yb)₂O₃) Mixing LaF₃Molecular weight of (D) is M (LaF)₃) GdF of₃Molecular weight of (2) is M (GdF)₃) YF will be₃Molecular weight of (2) is set to M (YF)₃) YbF₃Molecular weight of (2) is M (YbF)₃) The molecular weight of ZnO is M (ZnO), Li₂Molecular weight of O is set to M (Li)₂O), mixing Na₂The molecular weight of O is set to M (Na)₂O), mixing K with₂The molecular weight of O is set to M (K)₂O), ZrO prepared from₂Molecular weight of (2) is set to M (ZrO)₂) Is prepared from Nb₂O₅Molecular weight of (3) is M (Nb)₂O₅) Adding TiO to₂Molecular weight of (2) is M (TiO)₂) Introduction of WO₃Molecular weight of (1) is set to M (WO)₃) Mixing Ta₂O₅Molecular weight of (2) is M (Ta)₂O₅) Adding Bi₂O₃Molecular weight of (B) is M (Bi)₂O₃) The molecular weight of MgO is M (MgO), the molecular weight of CaO is M (CaO), the molecular weight of SrO is M (SrO), and the molecular weight of BaO is M (BaO).

The molecular weight of each oxide is the sum of the product of the number of atoms corresponding to cations contained in one molecule of the oxide and the atomic weight of the atoms and the product of the number of oxygen (O) contained in one molecule of the oxide and the atomic weight of oxygen, and corresponds to the formula weight. The molecular weight of each fluoride is the sum of the product of the number of atoms corresponding to a cation contained in one molecule of the fluoride and the atomic weight of the atom and the product of the number of fluorine (F) contained in one molecule of the fluoride and the atomic weight of fluorine. Further, the mass per 1mol of the molecule is a value obtained by adding a unit (g) to the molecular weight thereof. In table 1, the molecular weights of the oxides and fluorides are shown to the 3 th decimal place. For example, in the following description, the molecular weight may be a numerical value shown in table 1.

[ Table 1]

M(B₂O₃)	69.621
		M(SiO₂)	60.084
M(Al₂O₃)	101.961
		M(La₂O₃)	325.809
M(Gd₂O₃)	362.498
		M(Y₂O₃)	225.810
M(Yb₂O₃)	394.084
		M(ZnO)	81.389
M(Li₂O)	29.882
		M(Na₂O)	61.979
M(K₂O)	94.196
		M(ZrO₂)	123.223
M(Nb₂O₅)	265.810
		M(TiO₂)	79.882
M(WO₃)	231.839
		M(Ta₂O₅)	441.893
M(Bi₂O₃)	465.959
		M(MgO)	40.304
M(CaO)	56.077
		M(SrO)	81.389
M(BaO)	153.326
		M(LaF₃)	195.901
M(GdF₃)	214.245
		M(YF₃)	145.901
M(YbF₃)	230.050

Further, table 2 shows the number of cations contained in one molecule when the glass component is represented by an oxide or a fluoride.

[ Table 2]

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

In the optical glass of the present embodiment, the abbe number ν d is 39.0 or more and 45.0 or less, and the refractive index nd and the abbe number ν d satisfy the following formula (1).

nd≥2.235-0.01×νd···(1)

In the optical glass of the present embodiment, the lower limit of the abbe number ν d is 39.0, preferably 39.5, more preferably 40.0, and still more preferably 40.5. The upper limit of the abbe number ν d is 45.0, preferably 44.5, more preferably 44.0, and further preferably 43.5.

When the abbe number ν d is 39.0 or more, a material as an optical element is effective for correcting chromatic aberration. Further, when the abbe number ν d is larger than 45.0, if the refractive index nd is not lowered, the thermal stability of the glass is remarkably lowered and devitrification is easy in the process of manufacturing the glass. Further, by setting the refractive index nd within the range determined by the formula (1) with respect to the abbe's number ν d, an optical glass having high value in optical design can be produced. The upper limit of the refractive index nd is naturally determined in accordance with the above-mentioned composition range of the glass.

In the optical glass of the present embodiment, NWF1, RE1, and HR1 described later mean the total number of moles of the specific cation contained per 100g of the glass. Here, NWF1, RE1 and HR1 are indexes of the content of a specific glass component in the optical glass of the present invention, and symbols representing percentages such as mass% and% are not added, and are expressed only by numerical values. Hereinafter, details will be described by taking NWF1 as an example.

The NWF1 is expressed by the following equation 1.

[ mathematical formula 1]

Here, [ B ] in the above formula₂O₃/M(B₂O₃)]The denominator of (A) is boron oxide (B)₂O₃) Molecular weight of (B) is boron oxide (B)₂O₃) Is contained in mass%.

With respect to the molecule, in other words, boron oxide (B) in mass%₂O₃) The content of (B) is such that boron oxide (B) is contained per 100g of the glass₂O₃) The content of (c) is represented by mass (g).

Thus, [ B ] in the above formula₂O₃/M(B₂O₃)]Equivalent to boron oxide (B) contained per 100g of glass₂O₃) The number of moles of (a).

Further, the above-mentioned [ B ]₂O₃/M(B₂O₃)]Multiplication by 1 molecule of boron oxide (B)₂O₃) The cation (B) contained³⁺) Number of (2) [ < 2 > XB >₂O₃/M(B₂O₃)]Equivalent to boron ions (B) contained per 100g of glass³⁺) The number of moles of (a).

In addition, the aboveIn the formula [ SiO ]₂/M(SiO₂)]And [ 2X Al₂O₃/M(Al₂O₃)]Is also reacted with [2 XB₂O₃/M(B₂O₃)]The same applies.

Therefore, NWF1 represents the amount of boron ions (B) contained per 100g of glass³⁺) Silicon ion (Si)⁴⁺) And aluminum ion (Al)³⁺) The total value of the respective mole numbers of (a). Here, NWF1 is an index for the content of the network-forming component in the optical glass of the present invention, and is represented by a numerical value only.

HR1, RE1, and R1 described later are also the same as in NWF 1.

In the optical glass of the present embodiment, NWF1 is defined as described above. In addition, B₂O₃、SiO₂、Al₂O₃Functions as a network-forming component of the glass.

In the optical glass of the present embodiment, RE1 is a high-refractive-index low-dispersion component La expressed in mass%₂O₃、Gd₂O₃、Y₂O₃、Yb₂O₃、LaF₃、GdF₃、YF₃、YbF₃Each content of (a) is divided by the molecular weight of each oxide or fluoride, and multiplied by the total number of cations contained in each molecule (RE1 ═ 2 × La₂O₃/M(La2O₃)]+[2×Gd₂O₃/M(Gd₂O₃)]+[2×Y₂O₃/M(Y₂O₃)]+[2×Yb₂O₃/M(Yb₂O₃)]+[LaF₃/M(LaF₃)]+[GdF₃/M(GdF₃)]+[YF₃/M(YF₃)]+[YbF₃/M(YbF₃)]). That is, RE1 is La contained per 100g of glass³⁺、Gd³⁺、Y³⁺And Yb³⁺The total value of the respective mole numbers of (a). Here, RE1 is a high element in the optical glass of the present inventionThe index of the content of the dispersion component having a low refractive index is expressed by a numerical value.

As NWF1 decreases, the refractive index increases. When RE1 is increased, the refractive index can be raised without a large decrease in abbe number. Therefore, by increasing the ratio [ RE1/NWF1], the refractive index can be increased while maintaining the low dispersion characteristic.

In order to obtain the desired refractive index nd and Abbe's number vd, the ratio [ RE1/NWF1] in the optical glass of the present embodiment is 0.35 or more.

Further, in the optical glass of the present embodiment, the lower limit of the ratio [ RE1/NWF1] is preferably 0.36, and more preferably 0.37, 0.38, 0.39, 0.40, 0.41, 0.42, and 0.43 in this order.

In the optical glass of the present embodiment, the lower limit of the ratio [ RE1/NWF1] is set to the above range, whereby the refractive index nd and the abbe number ν d can be made to be desired values.

When NWF1 is increased, thermal stability of the glass is improved, and crystals are less likely to precipitate during glass production or glass forming. When RE1 is reduced, the thermal stability of the glass can be improved and crystals are not easily precipitated during the manufacturing process.

Therefore, in order to improve the thermal stability of the glass and obtain a glass in which crystals are less likely to precipitate, the upper limit of the ratio [ RE1/NWF1] is preferably 0.80, and more preferably 0.70, 0.60, 0.55, 0.54, 0.53, 0.52, and 0.51 in this order. By setting the upper limit of the ratio [ RE1/NWF1] to the above-described preferable range, the thermal stability of the glass can be further improved.

In the optical glass of the present embodiment, from the viewpoint of increasing the refractive index, the upper limit of NWF1 is preferably 0.80, and more preferably 0.75, 0.72, 0.70, 0.69, and 0.68 in this order. From the viewpoint of improving the thermal stability of the glass, the lower limit of NWF1 is preferably 0.45, and more preferably 0.48, 0.50, 0.53, 0.54, and 0.55 in this order.

In the optical glass of the present embodiment, from the viewpoint of improving the thermal stability of the glass, the upper limit of RE1 is preferably 0.37, more preferably 0.35, even more preferably 0.33, and even more preferably 0.31. From the viewpoint of increasing the refractive index without significantly decreasing the abbe number, the lower limit of RE1 is preferably 0.20, more preferably 0.22, even more preferably 0.24, and even more preferably 0.26.

As described above, an optical glass having an abbe number ν d of 39.0 or more and 45.0 or less has a refractive index satisfying the formula (1), and is significant in optical design. In general, when the refractive index of the glass is increased, the abbe number decreases and the dispersion increases. Therefore, in order to obtain the above optical characteristics, it is important to increase the refractive index while suppressing the decrease in the abbe number ν d as much as possible.

Rare earth oxide and Nb₂O₅、TiO₂、WO₃And Bi₂O₃All of them have the action of raising the refractive index of the glass, and Nb is larger than rare earth oxide₂O₅、TiO₂、WO₃And Bi₂O₃The effect of reducing the Abbe number (high dispersion effect) is strong.

However, in the precision press molding, if the glass reacts with the mold material of the press molding die, the transparency of the glass surface is lowered, and there is also a problem that the glass melts with the press molding die. In precision press molding, the substance that reacts with the mold material of the press molding mold is mainly a component that is liable to undergo valence change at high temperature among glass components, that is, Nb₂O₅、TiO₂、WO₃、Bi₂O₃. On the other hand, although rare earth oxide and Nb₂O₅、TiO₂、WO₃、Bi₂O₃It also has the effect of raising the refractive index, but it is similar to Nb₂O₅、TiO₂、WO₃、Bi₂O₃In contrast, the material is less likely to change in valence number at high temperature during precision press molding, and has low reactivity with the mold material. Thus, it is possible to provideIt is expected that the content of the rare earth oxide relative to Nb is a factor of chemical reaction between the glass and the mold material₂O₅、TiO₂、WO₃、Bi₂O₃The content of (A) is suppressed to a certain amount or less.

In the optical glass of the present embodiment, HR1 represents a high-refractive-index high-dispersion component Nb represented by mass%₂O₅、TiO₂、WO₃、Bi₂O₃Each value of the content (HR1 ═ 2 × Nb) is obtained by dividing each value by the molecular weight of each glass component and multiplying each value by the total number of cations contained in each molecule (HR1 ═ 2 × Nb)₂O₅/M(Nb₂O₅)]+[TiO₂/M(TiO₂)]+[WO₃/M(WO₃)]+[2×Bi₂O₃/M(Bi₂O₃)]). That is, HR1 is the amount of Nb contained per 100g of glass⁵⁺、Ti⁴⁺、W⁶⁺And Bi³⁺The total value of the respective mole numbers of (a). HR1 is an index for the content of the high-refractive-index high-dispersion component in the optical glass of the present invention, and is represented by numerical values only.

By reducing the ratio [ HR1/RE1] of HR1 to RE1, the lowering of abbe number can be suppressed, and further, the reaction between the glass and the mold material at the time of precision press molding can be suppressed, and the productivity of the precision press molded glass optical element can be improved.

For this reason, in the optical glass of the present embodiment, the ratio [ HR1/RE1] is 0.33 or less.

Further, in the optical glass of the present embodiment, the upper limit of the ratio [ HR1/RE1] is preferably 0.32, and more preferably 0.31, 0.30, 0.29, 0.28, 0.27, 0.25 in this order.

When the ratio [ HR1/RE1] is decreased, the thermal stability of the glass tends to be lowered, and the glass transition temperature tends to be increased. Further, since RE1 contributes to a larger increase in refractive index than HR1, it is preferably larger than [ HR1/RE1] within the above range from the viewpoint of producing a glass having a higher refractive index. Therefore, from the viewpoint of improving the thermal stability of the glass and lowering the glass transition temperature, or from the viewpoint of further increasing the refractive index, the lower limit of the ratio [ HR1/RE1] is preferably 0.04, and more preferably 0.08, 0.10, 0.11, 0.13, 0.15, and 0.16 in this order.

In the optical glass of the present embodiment, from the viewpoint of suppressing a decrease in abbe number and producing a high-quality optical element more stably by precision press molding, the upper limit of HR1 is preferably 0.100, and more preferably 0.090, 0.080, 0.070, and 0.060 in this order. From the viewpoint of further increasing the refractive index and further improving the thermal stability of the glass, the lower limit of HR1 is preferably 0.010, and more preferably 0.020, 0.030, and 0.040 in this order.

<Nb₂O₅/(Nb₂O₅+Ta₂O₅)>

In the optical glass of the present embodiment, Nb₂O₅Relative to the content of Nb₂O₅And Ta₂O₅The mass ratio of the total content of [ Nb ]₂O₅/(Nb₂O₅+Ta₂O₅)]Is above 2/3. That is, the optical glass of the present embodiment contains Nb₂O₅And is prepared by reacting Nb₂O₅Is set to Ta₂O₅More than 2 times of the content of (A).

Further, in the optical glass of the present embodiment, the mass ratio [ Nb ]₂O₅/(Nb₂O₅+Ta₂O₅)]The lower limit of (b) is preferably 0.67, and more preferably 0.70, 0.80, 0.90, 0.95, 0.98 and 0.99 in this order. Further, mass ratio [ Nb₂O₅/(Nb₂O₅+Ta₂O₅)]The upper limit of (b) is preferably 1.00.

By mixing the mass ratio [ Nb₂O₅/(Nb₂O₅+Ta₂O₅)]The lower limit of (A) is within the above range, whereby the lowering of the refractive index can be suppressed and the thermal stability of the glass can be maintained. Further, by setting the mass ratio [ Nb₂O₅/(Nb₂O₅+Ta₂O₅)]Is in the above range, and can also be compared with Nb₂O₅In an amount of Ta₂O₅The content of (3) is relatively reduced to reduce the amount of use of very expensive Ta.

Generally, a glass having low-temperature softening properties suitable for precision press molding contains Li having an action of lowering the glass transition temperature Tg₂O、Na₂O、K₂O or ZnO. In particular, Li, which has a strong effect of lowering the glass transition temperature Tg, is used in such a glass₂The contents of O and ZnO are high. However, these glass components are easily volatilized from the molten glass in the process of manufacturing the glass.

When a specific glass component, that is, a volatile glass component is selectively volatilized from a molten glass, the composition ratio of the glass is changed, and the characteristics such as the refractive index nd and the abbe number ν d cannot be set to desired values. As a result, it is difficult to stably produce glass having desired characteristics. Further, if a specific glass component is volatilized from the surface of a high-temperature glass at the time of molding the molten glass, an optical inhomogeneous portion called a streak is generated on the surface of the glass. In an optical glass requiring high homogeneity, the occurrence of such striae is not preferable.

The inventors of the present application have found through investigation that the volatility of molten glass depends on volatile Li₂O、Na₂O、K₂Content of O and ZnO and non-volatile La₂O₃、Gd₂O₃、Y₂O₃And Yb₂O₃The content ratio of the rare earth oxide(s) in (b).

In the optical glass of the present embodiment, D1 represents Li to be represented by mass%₂O、Na₂O and K₂The value of each content of O is divided by the molecular weight of each glass component and multiplied by the cation contained in each moleculeThe total of the number of seeds and the value of 3 and the value obtained by dividing the value of the ZnO content expressed in mass% by the molecular weight and multiplying the value by the number of cations contained in the molecule (D1 ═ 2 × Li₂O/M(Li₂O)]×3+[2×Na₂O/M(Na₂O)]×3+[2×K₂O/M(K₂O)]×3+[ZnO/M(ZnO)]). Multiplication by 3 is due to Li₂O、Na₂O and K₂O is more volatile than ZnO. That is, D1 can be expressed as D1 { [2 × Li { ]₂O/M(Li₂O)]+[2×Na₂O/M(Na₂O)]+[2×K₂O/M(K₂O)]}×3+[ZnO/M(ZnO)]. D1 is an index for the content of volatile components in the optical glass of the present invention and is represented by numerical values only.

D1 is a numerical value of a factor that promotes volatilization of molten glass. On the other hand, RE1 is a numerical value of a factor for suppressing volatilization of molten glass. That is, by increasing the ratio of RE1 to D1 [ RE1/D1], volatilization of molten glass can be suppressed.

Thus, the ratio [ RE1/D1] is an index indicating the volatility of molten glass, i.e., molten glass. By setting the ratio [ RE1/D1] to 0.90 or more, volatilization of the molten glass can be suppressed. As a result, optical glass having desired characteristics can be stably produced. Further, high homogeneity of the glass can be maintained. Therefore, in the optical glass of the present embodiment, the ratio [ RE1/D1] is 0.90 or more.

Further, from the viewpoint of suppressing volatilization of the molten glass, in the optical glass of the present embodiment, the lower limit of the ratio [ RE1/D1] is preferably 0.95, and more preferably 0.98, 1.00, 1.05, 1.10, 1.12, and 1.13 in this order.

On the other hand, when the ratio [ RE1/D1] is decreased, the glass transition temperature Tg is decreased, and the temperature of the glass at the time of precision press molding is decreased. As a result, the reaction between the glass and the press mold is less likely to occur during precision press molding, the transparency of the glass surface after press molding is easily maintained, and fusion between the glass and the press mold is easily suppressed. From such a viewpoint, the upper limit of the ratio [ RE1/D1] is preferably 2.5, and more preferably 2.3, 2.2, 2.15, 2.10, 2.08, and 2.07 in this order.

From the viewpoint of suppressing volatilization of the molten glass, in the optical glass of the present embodiment, the upper limit of D1 is preferably 0.33, and more preferably 0.30, 0.28, 0.26, and 0.25 in this order. On the other hand, from the viewpoint of lowering the glass transition temperature, the lower limit of D1 is preferably 0.05, and more preferably 0.08, 0.10, 0.12, and 0.13 in this order.

The glass component is roughly divided into a component having an action of relatively lowering the glass transition temperature Tg and a component having an action of relatively raising the glass transition temperature Tg. The component having the effect of relatively lowering the glass transition temperature Tg is mainly Li₂O、Na₂O、K₂O、ZnO、MgO、CaO、SrO、BaO、B₂O₃、Nb₂O₅、TiO₂、WO₃、Bi₂O₃、Ta₂O₅. On the other hand, the component having the effect of relatively increasing the glass transition temperature Tg with respect to the glass component is mainly SiO₂、Al₂O₃、ZrO₂、La₂O₃、Gd₂O₃、Y₂O₃、Yb₂O₃、LaF₃、GdF₃、YF₃、YbF₃。

As a result of studies by the inventors of the present application, it was found that there is a correlation between the ratio [ L1/(NWF1+ RE1) ] of L1 to the total value of NWF1 and RE1 and the glass transition temperature Tg, where L1 is a total value obtained by dividing the value of each content of the above-mentioned glass components expressed in mass% by the molecular weight of each glass component, multiplying the value by the number of cations contained in each molecule, and further multiplying the value by the influence of each glass component on the glass transition temperature Tg as a coefficient. Table 3 shows coefficients indicating the influence of the glass components on the glass transition temperature Tg.

[ Table 3]

Such an L1 can be represented as

L1＝[10×2×Li₂O/M(Li₂O)]+[8×2×Na₂O/M(Na₂O)]+[4×2×K₂O/M(K₂O)]+[4×1×ZnO/M(ZnO)]+[1×1×MgO/M(MgO)]+[2×1×CaO/M(CaO)]+[2×1×SrO/M(SrO)]+[2×1×BaO/M(BaO)]+[1×2×B₂O₃/M(B₂O₃)]+[1×2×Nb₂O₅/M(Nb₂O₅)]+[1×1×TiO₂/M(TiO₂)]+[4×1×WO₃/M(WO₃)]+[4×2×Bi₂O₃/M(Bi₂O₃)]+[1×2×Ta₂O₅/M(Ta₂O₅)]+[-2×1×SiO₂/M(SiO₂)]+[-1×2×Al₂O₃/M(Al₂O₃)]+[-2×1×ZrO₂/M(ZrO₂)]+[-1×2×La₂O₃/M(La₂O₃)]+[-1×2×Gd₂O₃/M(Gd₂O₃)]+[-1×2×Y₂O₃/M(Y₂O₃)]+[-1×2×Yb₂O₃/M(Yb₂O₃)]+[-1×1×LaF₃/M(LaF₃)]+[-1×1×GdF₃/M(GdF₃)]+[-1×1×YF₃/M(YF₃)]+[-1×1×YbF₃/M(YbF₃)]。

That is, the value L1 can be expressed as

L1＝[20×Li₂O/M(Li₂O)]+[16×Na₂O/M(Na₂O)]+[8×K₂O/M(K₂O)]+[4×ZnO/M(ZnO)]+[MgO/M(MgO)]+[2×CaO/M(CaO)]+[2×SrO/M(SrO)]+[2×BaO/M(BaO)]+[2×B₂O₃/M(B₂O₃)]+[2×Nb₂O₅/M(Nb₂O₅)]+[TiO₂/M(TiO₂)]+[4×WO₃/M(WO₃)]+[8×Bi₂O₃/M(Bi₂O₃)]+[2×Ta₂O₅/M(Ta₂O₅)]-[2×SiO₂/M(SiO₂)]-[2×Al₂O₃/M(Al₂O₃)]-[2×ZrO₂/M(ZrO₂)]-[2×La₂O₃/M(La₂O₃)]-[2×Gd₂O₃/M(Gd₂O₃)]-[2×Y₂O₃/M(Y₂O₃)]-[2×Yb₂O₃/M(Yb₂O₃)]-[LaF₃/M(LaF₃)]-[GdF₃/M(GdF₃)]-[YF₃/M(YF₃)]-[YbF₃/M(YbF₃)]。

L1 is an index for the content of components affecting the glass transition temperature Tg in the optical glass of the present invention, and is represented by numerical values only.

Fig. 1 is a graph in which the horizontal axis represents a ratio of L1 to the total value of NWF1 and RE1 [ L1/(NWF1+ RE1) ], and the vertical axis represents a glass transition temperature Tg, and the ratio [ L1/(NWF1+ RE1) ] and the glass transition temperature Tg are plotted for a known glass, where NWF1 corresponds to a network-forming component in a glass component, and RE1 corresponds to a rare-earth oxide and a rare-earth fluoride. As is clear from fig. 1, the points are substantially distributed on a straight line, and it is understood that the ratio [ L1/(NWF1+ RE1) ] has a correlation with the glass transition temperature Tg.

That is, the glass transition temperature Tg decreases with an increase in the ratio [ L1/(NWF1+ RE1) ], and increases with a decrease in the ratio [ L1/(NWF1+ RE1) ].

In this manner, by increasing the ratio [ L1/(NWF1+ RE1) ], the glass transition temperature Tg can be lowered, and a glass suitable for precision press molding, that is, a glass having low-temperature softening properties can be provided. Further, by increasing the ratio [ L1/(NWF1+ RE1) ], the meltability of the glass can be improved, that is, the glass raw material does not cause a melt residue, and a homogeneous glass can be provided.

In order to obtain an optical glass having low-temperature softening properties and good melting properties, the ratio [ L1/(NWF1+ RE1) ] is 0.78 or more in the optical glass of the present embodiment.

Further, in the optical glass of the present embodiment, the lower limit of the ratio [ L1/(NWF1+ RE1) ] is preferably 0.80, and more preferably 0.85, 0.90, 0.91, 0.92, 0.95, 1.00, and 1.05 in this order.

By setting the lower limit of the ratio [ L1/(NWF1+ RE1) ] to the above range, it is possible to obtain low-temperature softening properties suitable for precision press molding and to improve the meltability of glass. When the ratio [ L1/(NWF1+ RE1) ] is too large, the thermal stability of the glass tends to be lowered, and the refractive index tends to be lowered. From the viewpoint of maintaining the desired refractive index and thermal stability, the upper limit of the ratio [ L1/(NWF1+ RE1) ] is preferably 2, and more preferably 1.8, 1.6, and 1.5 in this order.

In the optical glass of the present embodiment, R1 is a total value obtained by dividing the numerical value of each content of the alkaline earth metal oxides MgO, CaO, SrO, and BaO in mass% by the value of the molecular weight of each glass component (R1 ═ MgO/m (MgO))]+[CaO/M(CaO)]+[SrO/M(SrO)]+[BaO/M(BaO)]). That is, R1 is Mg contained per 100g of glass²⁺、Ca²⁺、Sr² ⁺And Ba²⁺The total value of the respective mole numbers of (a). R1 is an index for the content of the alkaline earth metal oxide in the optical glass of the present invention, and is represented by numerical values only.

Forming a network into component B₂O₃、SiO₂、Al₂O₃The network-forming component has a larger effect of suppressing the decrease in the abbe number than the alkaline earth metal oxide, MgO, CaO, SrO, BaO.

Therefore, the upper limit of the ratio [ R1/NWF1] of R1 to NWF1 is preferably 0.30, and more preferably 0.25, 0.20, 0.19, 0.15, 0.10, 0.05, and 0.02 in this order. The lower limit of the ratio [ R1/NWF1] is preferably 0. The ratio [ R1/NWF1] may be 0.

By setting the upper limit of the ratio [ R1/NWF1] to the above range, the decrease in abbe number can be suppressed.

< glass composition >

Hereinafter, the glass composition will be described in detail. Unless otherwise specified, the contents of various glass components and the like are expressed in mass%. The total content is the total content of the contents of the plurality of glass components, and includes the case where each content is 0%.

In the optical glass of the present embodiment, B₂O₃The upper limit of the content of (b) is preferably 32%, and more preferably 30%, 28%, 26%, 25%, and 24% in this order. In addition, B₂O₃The lower limit of the content of (b) is preferably 10%, and more preferably 13%, 14%, 15%, and 16% in this order.

B₂O₃Is a network-forming component of the glass, and has the effects of improving the meltability of the glass and suppressing the decrease in Abbe number. Furthermore, with SiO₂The glass transition temperature Tg is less likely to increase than the above. When B is present₂O₃When the content (b) is small, the thermal stability and meltability of the glass tend to be low. On the other hand, when B₂O₃When the content (d) is large, the refractive index nd and chemical durability tend to be low. Therefore, from the viewpoint of improving the thermal stability, meltability, moldability and the like of the glass, B is preferable₂O₃The lower limit of the content of (B) is the above range. On the other hand, from the viewpoint of obtaining a desired refractive index while maintaining chemical durability well, B₂O₃The upper limit of the content of (b) is preferably the above range.

In the optical glass of the present embodiment, SiO₂The upper limit of the content of (b) is preferably 10%, and more preferably 8%, 7%, 6%, 5%, 4%, and 3% in this order. Furthermore, SiO₂The lower limit of the content of (b) is preferably 0%. In addition, SiO₂The content of (B) may be 0%.

SiO₂Being meshes of glassThe complex-forming component has the effects of improving the chemical durability and weather resistance of the glass, increasing the viscosity of the molten glass, and facilitating the molding of the molten glass into glass. When SiO is present₂When the content (b) is small, the thermal stability and chemical durability of the glass tend to be lowered. On the other hand, when SiO₂When the amount of (B) is large, the meltability and low-temperature softening property of the glass tend to be lowered, that is, the glass transition temperature tends to be increased, and the glass raw material tends to be melted and left. Therefore, SiO is used for improving the meltability and low-temperature softening property of the glass₂The upper limit of the content of (b) is preferably the above range.

In the optical glass of the present embodiment, Al₂O₃The upper limit of the content of (b) is preferably 5%, and more preferably 4%, 3%, 2.5%, 2%, 1.5%, 1%, 0.5%, 0.1% in this order. Further, Al₂O₃The lower limit of the content of (b) is preferably 0%. In addition, Al₂O₃The content of (B) may be 0%.

Al₂O₃The glass component having an effect of improving the chemical durability and weather resistance of the glass may be considered as a network-forming component. However, when Al is used₂O₃When the content of (b) is increased, problems such as a decrease in refractive index nd, a decrease in thermal stability of the glass, an increase in glass transition temperature Tg, and a decrease in meltability tend to occur. From the viewpoint of avoiding such a problem, Al₂O₃The upper limit of the content of (b) is preferably the above range.

In the optical glass of the present embodiment, the network-forming component B of the glass₂O₃、SiO₂And Al₂O₃Total content of [ B ]₂O₃+SiO₂+Al₂O₃]The upper limit of (b) is preferably 34%, and more preferably 32%, 30%, 28%, 26%, 25%, and 24% in this order. Further, the total content [ B ]₂O₃+SiO₂+Al₂O₃]The lower limit of (b) is preferably 10%, and more preferably 13%, 15%, 17%, 18%, and 19% in this order.

By adding the total content [ B ]₂O₃+SiO₂+Al₂O₃]The upper limit of (b) is set to the above range, so that the refractive index can be easily maintained in a desired range. Further, by adding the total content [ B ]₂O₃+SiO₂+Al₂O₃]The lower limit of (b) is set to the above range, whereby the thermal stability of the glass can be improved and devitrification of the glass can be easily suppressed.

In the optical glass of the present embodiment, B₂O₃Relative to B₂O₃、SiO₂And Al₂O₃The mass ratio of the total content of [ B ]₂O₃/(B₂O₃+SiO₂+Al₂O₃)]The lower limit of (b) is preferably 0.50, and more preferably 0.60, 0.70, 0.80, and 0.85 in this order. The mass ratio [ B ] can also be determined₂O₃/(B₂O₃+SiO₂+Al₂O₃)]Is set to 1.

When mass ratio [ B ]₂O₃/(B₂O₃+SiO₂+Al₂O₃)]When the glass is small, the glass tends to have a low melting property and a high glass transition temperature Tg. Therefore, the mass ratio [ B ] is set so that good meltability and low-temperature softening property of the glass are maintained₂O₃/(B₂O₃+SiO₂+Al₂O₃)]The lower limit of (b) is preferably in the above range.

The mass ratio [ B ] can also be determined₂O₃/(B₂O₃+SiO₂+Al₂O₃)]Set to 1, but by containing a small amount of SiO₂Therefore, the viscosity of the molten glass during molding can be easily adjusted to a viscosity suitable for molding.

In the optical glass of the present embodiment, La₂O₃、Gd₂O₃、Y₂O₃And Yb₂O₃Total content of [ La ]₂O₃+Gd₂O₃+Y₂O₃+Yb₂O₃]The upper limit of (b) is preferably 65%, and more preferably 60%, 57%, 55%, 53%, and 52% in this order. Further, the total content [ La ]₂O₃+Gd₂O₃+Y₂O₃+Yb₂O₃]The lower limit of (b) is preferably 35%, and more preferably 38%, 41%, 44%, 45%, and 46% in this order.

The total content [ La ] is such that the desired refractive index and Abbe number are achieved₂O₃+Gd₂O₃+Y₂O₃+Yb₂O₃]The lower limit of (b) is preferably in the above range. The total content [ La ] is in order to improve the thermal stability and low-temperature softening property of the glass₂O₃+Gd₂O₃+Y₂O₃+Yb₂O₃]The upper limit of (b) is preferably in the above range.

In the optical glass of the present embodiment, La₂O₃The upper limit of the content of (b) is preferably 50%, and more preferably 45%, 42%, 40%, 38%, and 37% in this order. Further, La₂O₃The lower limit of the content of (b) is preferably 10%, and more preferably 15%, 17%, 19%, 20%, 21%, 22% in this order.

La₂O₃In addition to the above-described effects, the glass composition has an effect of improving the chemical durability of the glass. Further, among the rare earth oxide components, La₂O₃Is a component which is less likely to lower thermal stability even when the content is large. Therefore, from the viewpoint of improving the thermal stability and chemical durability of the glass, La₂O₃The lower limit of the content of (b) is preferably the above range. Further, from the viewpoint of improving the thermal stability of the glass, La₂O₃The upper limit of the content of (b) is preferably the above range.

In the optical glass of the present embodiment, Gd₂O₃The upper limit of the content of (b) is preferably 50%, and more preferably 45%, 40%, 35%, 31%, 30%, and 29% in this order. In addition, Gd₂O₃In the following amountThe limit is preferably 1%, and more preferably 2%, 3%, 5%, 7%, 10%, 11%, and 12% in this order.

Gd₂O₃In addition to the above-described effects, the glass composition has an effect of improving the chemical durability of the glass. Further, Gd₂O₃By reacting with La in glass₂O₃Coexisting, thereby also having an effect of improving the thermal stability of the glass. Therefore, Gd is effective in improving the thermal stability and chemical durability of the glass₂O₃The lower limit of the content of (b) is preferably the above range. In addition, Gd is added from the viewpoint of improving the thermal stability of the glass₂O₃The upper limit of the content of (b) is preferably the above range.

In the optical glass of the present embodiment, Y is₂O₃The upper limit of the content of (b) is preferably 10%, and more preferably 8%, 5%, 4%, and 3% in this order. Furthermore, Y₂O₃The lower limit of the content of (b) is preferably 0%. In addition, Y₂O₃The content of (B) may be 0%.

Y₂O₃In addition to the above-described effects, the glass composition has an effect of improving the chemical durability of the glass. Further, Y₂O₃By reacting with La in glass₂O₃Coexisting, thereby also having an effect of improving the thermal stability of the glass. Therefore, from the viewpoint of improving the thermal stability of the glass, Y₂O₃The content of (b) is preferably in the above range.

In the optical glass of the present embodiment, Yb₂O₃The upper limit of the content of (b) is preferably 3%, and more preferably 2.5%, 2%, 1.5%, 1%, 0.5%, 0.1%, 0.05% in this order. In addition, Yb₂O₃The lower limit of the content of (b) is preferably 0%. In addition, Yb₂O₃The content of (B) may be 0%.

Yb₂O₃And La₂O₃、Gd₂O₃And Y₂O₃Also has the advantage of increasing without greatly reducing the Abbe numberGlass composition of the effect of refractive index. But with La₂O₃、Gd₂O₃、Y₂O₃Comparative Yb₂O₃Has a large molecular weight, and therefore, the specific gravity of the glass increases. When the specific gravity of the glass increases, the mass of the optical element increases. For example, if a lens having a large mass is incorporated in an image pickup lens of an auto focus type, power required for driving the lens at the time of auto focus increases, and battery consumption increases. Therefore, it is desired to reduce Yb₂O₃To suppress the increase in specific gravity of the glass.

In addition, Yb₂O₃Has absorption in the near infrared region. Thus, Yb₂O₃The glass containing a large amount of (B) is not preferable for applications requiring high transmittance in the near infrared region, such as surveillance cameras and night vision cameras, because of its high light absorption in the near infrared region. From the viewpoint of improving such a problem, Yb₂O₃The content of (b) is preferably in the above range.

In the optical glass of the present embodiment, LaF₃The upper limit of the content of (b) is not particularly limited, and is preferably 5%, and more preferably 3%, 2%, 1%, and 0.5% in this order. Furthermore, LaF₃The content of (B) may be 0%.

In the optical glass of the present embodiment, GdF₃The upper limit of the content of (b) is not particularly limited, and is preferably 5%, and more preferably 3%, 2%, 1%, and 0.5% in this order. Furthermore, GdF₃The content of (B) may be 0%.

In the optical glass of the present embodiment, YF₃The upper limit of the content of (b) is not particularly limited, and is preferably 5%, and more preferably 3%, 2%, 1%, and 0.5% in this order. Further, YF₃The content of (B) may be 0%.

In the optical glass of the present embodiment, YbF₃Upper limit of the content of (B)The content of the halide is not particularly limited, and is preferably 3%, and more preferably 2%, 1%, and 0.5% in this order. Further, YbF₃The content of (B) may be 0%.

In the optical glass of the present embodiment, La₂O₃Relative to La₂O₃、Gd₂O₃、Y₂O₃And Yb₂O₃Total content of [ La ]₂O₃+Gd₂O₃+Y₂O₃+Yb₂O₃]Mass ratio of [ La ]₂O₃/(La₂O₃+Gd₂O₃+Y₂O₃+Yb₂O₃)]The upper limit of (b) is preferably 0.99, and more preferably 0.95, 0.90, 0.85, 0.80, 0.76, 0.74, 0.73 in this order. Further, mass ratio [ La ]₂O₃/(La₂O₃+Gd₂O₃+Y₂O₃+Yb₂O₃)]The lower limit of (b) is preferably 0.3, and more preferably 0.35, 0.4, 0.45, and 0.46 in this order.

By making the mass ratio [ La ] of₂O₃/(La₂O₃+Gd₂O₃+Y₂O₃+Yb₂O₃)]The upper limit of (b) is in the above range, whereby thermal stability and meltability can be maintained in a good state. Further, by making the mass ratio [ La ]₂O₃/(La₂O₃+Gd₂O₃+Y₂O₃+Yb₂O₃)]The lower limit of (b) is in the above range, so that thermal stability and meltability can be maintained in a good state.

In the optical glass of the present embodiment, the upper limit of the content of ZnO is preferably 25%, and more preferably 22%, 20%, 18%, 17%, and 16% in this order. The lower limit of the ZnO content is preferably 5%, and more preferably 8%, 9%, 10%, and 11% in this order.

ZnO is a glass component having an action of lowering the glass transition temperature Tg while maintaining the refractive index and an action of promoting melting of raw materials of the glass (i.e., an action of improving meltability) when melting the glass. In addition, ZnO has a strong effect of improving the thermal stability of glass and lowering the liquidus temperature, as compared with other divalent metal components such as alkaline earth metals. However, when the content of ZnO is increased, abbe number ν d tends to decrease, and the glass tends to be highly dispersed. Therefore, the lower limit of the ZnO content is preferably in the above range from the viewpoint of lowering the glass transition temperature Tg and improving the meltability and thermal stability of the glass. From the viewpoint of reducing the dispersion of the glass, the upper limit of the content of ZnO is preferably in the above range.

In the optical glass of the present embodiment, Li₂The upper limit of the content of O is preferably 4.0%, and more preferably 3.0%, 2.0%, 1.6%, 1.2%, 0.8%, 0.4% in this order. Furthermore, Li₂The lower limit of the content of O is preferably 0%.

Li₂O is a glass component which has a strong action of lowering the glass transition temperature Tg and is useful for obtaining low-temperature softening properties. Furthermore, Li₂O also plays a role in improving the meltability of the glass. On the other hand, when Li₂When the content of O is increased, the refractive index nd tends to decrease. Therefore, Li is from the viewpoint of lowering the glass transition temperature Tg while maintaining the desired optical characteristics₂The content of O is preferably in the above range.

In the optical glass of the present embodiment, ZrO₂The upper limit of the content of (b) is preferably 15%, and more preferably 12%, 10%, 8%, 7%, and 6% in this order. Furthermore, ZrO₂The lower limit of the content of (b) is preferably 0.1%, and more preferably 0.5%, 1.0%, 1.5%, 2.0%, 2.5%, 3.0% in this order.

ZrO₂A glass component having the effect of increasing the refractive index nd and improving the thermal stability of the glass. However, when ZrO₂When the content (c) is too large, the thermal stability of the glass tends to be lowered, the glass transition temperature Tg tends to be increased, and the glass raw material tends to be melted and left. Thus, vitrification can be suppressedFrom the viewpoints of increasing the transition temperature Tg, maintaining good melting properties and thermal stability of the glass, and realizing desired optical properties, ZrO₂The upper limit of the content of (b) is preferably the above range. On the other hand, from the viewpoint of improving the thermal stability of the glass while achieving desired optical characteristics, ZrO₂The lower limit of the content of (b) is preferably the above range.

In the optical glass of the present embodiment, Nb₂O₅The upper limit of the content of (b) is preferably 15%, and more preferably 12%, 10%, 9%, 8%, 7%, and 6% in this order. Further, Nb₂O₅The lower limit of the content of (b) is preferably 0.1%, and more preferably 0.3%, 0.5%, 1.0%, 1.2%, 1.5%, 2.0% in this order.

Nb₂O₅Has the effects of increasing the refractive index and improving the thermal stability of the glass. In addition, it has an effect of improving the chemical durability of the glass. Nb₂O₅Is a substitution for Ta having a high refractive index and a low dispersion characteristic and having a large effect of improving the thermal stability of glass₂O₅The glass component (B) is Ta which is extremely expensive and has an effect of lowering the meltability of the glass₂O₅The content of (a) is important.

When Nb₂O₅When the content (c) is too large, the glass tends to have low thermal stability, and the abbe number ν d tends to be small, resulting in high glass dispersion. Further, the coloring of the glass tends to be strong. Therefore, from the viewpoint of maintaining the thermal stability of the glass, Nb₂O₅The lower limit of the content of (b) is preferably the above range. On the other hand, from the viewpoint of maintaining the thermal stability of the glass and suppressing the increase in coloring of the glass, Nb₂O₅The upper limit of the content of (b) is preferably the above range.

In the optical glass of the present embodiment, Ta₂O₅The upper limit of the content of (b) is preferably 3%, and more preferably 2.5%, 2%, 1.5%, 1%, 0.5%, 0.3%, 0.2%, 0.1%, 0.05% in this order. Further, Ta₂O₅The lower limit of the content of (b) is preferably 0%. In addition, Ta₂O₅The content of (B) may be 0%.

As mentioned above, Ta₂O₅The glass composition has a high refractive index and low dispersion characteristics and has an effect of improving the thermal stability of the glass. Ta compared with other glass compositions₂O₅Is an extremely expensive component when Ta₂O₅When the content of (b) is increased, the production cost of the glass is increased. Further, Ta is compared with other glass components₂O₅The molecular weight of (2) increases the specific gravity of the glass, and as a result, the weight of the glass optical element increases. Further, when Ta is used₂O₅When the content of (b) is increased, the meltability of the glass is lowered, and the glass raw material is likely to remain molten when the glass is melted. Thus, Ta₂O₅The content of (b) is preferably in the above range.

In the optical glass of the present embodiment, Nb₂O₅、TiO₂、WO₃And Bi₂O₃Total content of [ Nb ]₂O₅+TiO₂+WO₃+Bi₂O₃]The upper limit of (b) is preferably 15%, and more preferably 13%, 12%, 11%, 10%, 9%, 8%, 7% in this order. Further, the total content [ Nb ]₂O₅+TiO₂+WO₃+Bi₂O₃]The lower limit of (b) is preferably 0.1%, and more preferably 0.3%, 0.5%, 1%, 1.2%, 1.5%, 2%, 3%, 4%, 5% in this order.

TiO₂、WO₃And Bi₂O₃And Nb₂O₅Also, the glass component having the effect of increasing the refractive index also has the effect of improving the thermal stability of the glass by containing it in an appropriate amount. Further, when the content of these glass components is increased, the abbe number ν d is decreased. Therefore, these glass components are referred to as high-refractive-index high-dispersion components. The total content [ Nb ] is from the viewpoint of suppressing decrease in Abbe number ν d and suppressing increase in coloring of glass₂O₅+TiO₂+WO₃+Bi₂O₃]The upper limit of (b) is preferably in the above range. Further, from the viewpoint of improving the thermal stability of the glass while maintaining a high refractive index, the total content [ Nb ]₂O₅+TiO₂+WO₃+Bi₂O₃]The lower limit of (b) is preferably in the above range.

In the optical glass of the present embodiment, TiO₂、WO₃And Bi₂O₃Total content of [ TiO ]₂+WO₃+Bi₂O₃]The upper limit of (b) is preferably 15%, and more preferably 12%, 10%, 9%, 8%, 7%, 6.5% in this order. Further, the total content [ TiO₂+WO₃+Bi₂O₃]The lower limit of (b) is preferably 0%, and more preferably 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3% in this order.

In the high refractive index and high dispersion component, Nb is added₂O₅In contrast, TiO₂、WO₃And Bi₂O₃The coloring of the glass tends to increase. The total content [ TiO ] is from the viewpoint of suppressing an increase in coloring of the glass₂+WO₃+Bi₂O₃]The upper limit of (b) is preferably in the above range.

In the optical glass of the present embodiment, WO₃The upper limit of the content of (b) is preferably 15%, and more preferably 13%, 12%, 11%, 10%, 9%, 8%, 7% in this order. Furthermore, WO₃The lower limit of the content of (b) is preferably 0%, and more preferably 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3% in this order.

Among the components having high refractive index and high dispersion, WO₃Has the effect of lowering the glass transition temperature Tg. However, when WO is used₃When the content of (b) is too large, the abbe number ν d decreases, and it becomes difficult to realize desired optical characteristics. In addition, the coloration of the glass may increase. From the viewpoints of suppressing decrease in Abbe's number ν d and preventing increase in coloring of glass, WO₃The upper limit of the content of (b) is preferably the above range. In addition, WO₃The content of (B) can also be 0%. Furthermore, in order to obtain WO₃WO, the effect of suppressing the increase of the glass transition temperature Tg₃The lower limit of the content of (b) is preferably the above range.

In the optical glass of the present embodiment, TiO₂The upper limit of the content of (b) is preferably 5%, and more preferably 4%, 3%, 2.5%, 2%, 1.5%, 1%, 0.5%, 0.1% in this order. Furthermore, TiO₂The lower limit of the content of (b) is preferably 0%. In addition, TiO₂The content of (B) may be 0%.

In the high refractive index and high dispersion component, TiO₂The glass composition is a glass composition which can increase the coloring of glass relatively easily. Furthermore, TiO₂In the precision press molding, a reaction occurs with the molding surface of the press mold, and as a result, the transparency of the surface of the glass after press molding is lowered (white turbidity), and minute bubbles are likely to be generated on the surface of the glass. Therefore, TiO compounds are used for producing optical elements having less coloring and good surface quality₂The content of (b) is preferably in the above range.

In the optical glass of the present embodiment, Bi₂O₃The upper limit of the content of (b) is preferably 5%, and more preferably 4%, 3%, 2.5%, 2%, 1.5%, 1%, 0.5%, 0.1% in this order. In addition, Bi₂O₃The lower limit of the content of (b) is preferably 0%. In addition, Bi₂O₃The content of (B) may be 0%.

Among the high refractive index and high dispersion components, Bi₂O₃The molecular weight of (2) is a glass component which increases the specific gravity of the glass and the coloring of the glass, so that it is preferable to reduce Bi₂O₃The content of (a). Thus, Bi₂O₃The content of (b) is preferably in the above range.

In the optical glass of the present embodiment, Na₂The upper limit of the content of O is preferably 5%, and more preferably 4%, 3%, 2.5%, 2%, 1.5%, 1%, 0.5%, 0.1% in this order. Further, Na₂The lower limit of the content of O is preferably 0%. In addition, Na₂The content of O may be 0%.

In the optical glass of the present embodiment, K₂The upper limit of the content of O is preferably 5%, and more preferably 4%, 3%, 2.5%, 2%, 1.5%, 1%, 0.5%, 0.1% in this order. Furthermore, K₂The lower limit of the content of O is preferably 0%. In addition, K₂The content of O may be 0%.

Na₂O and K₂O has an effect of improving the meltability of the glass, but when the content thereof is increased, the refractive index nd, the thermal stability, the chemical durability and the weather resistance of the glass are lowered. Thus, Na₂O and K₂The respective contents of O are preferably set to the above ranges.

In the optical glass of the present embodiment, Li₂O、Na₂O and K₂Total content of O [ Li₂O+Na₂O+K₂O]The upper limit of (b) is preferably 6%, and more preferably 4%, 3%, 2.5%, 2%, 1.5%, 1% in this order. Further, the total content [ Li₂O+Na₂O+K₂O]The lower limit of (B) is preferably 0%.

Li₂O is a glass component which has a strong action of lowering the glass transition temperature Tg and is useful for obtaining low-temperature softening properties. Furthermore, Li₂O also plays a role in improving the meltability of the glass. On the other hand, when Li₂When the content of O is increased, the refractive index nd tends to decrease. Further, Na₂O and K₂O has an effect of improving the meltability of the glass, but when their content is increased, the refractive index nd, the thermal stability, the chemical durability, and the weather resistance of the glass are lowered. Thus, Li₂O、Na₂O and K₂Total content of O [ Li₂O+Na₂O+K₂O]Preferably within the above range.

In the optical glass of the present embodiment, Rb₂The upper limit of the content of O is preferably 3%, and more preferably 2.5%, 2%, 1.5%, 1%, 0.5%, 0.1% in this order. In addition, Rb₂The lower limit of the content of O is preferably 0%.In addition, Rb₂The content of O may be 0%.

In the optical glass of the present embodiment, Cs₂The upper limit of the content of O is preferably 3%, and more preferably 2.5%, 2%, 1.5%, 1%, 0.5%, 0.1% in this order. In addition, Cs₂The lower limit of the content of O is preferably 0%. In addition, Cs₂The content of O may be 0%.

Rb₂O and Cs₂O has an effect of improving the meltability of the glass, but when the content thereof is increased, the refractive index nd, the thermal stability, the chemical durability and the weather resistance of the glass are lowered. Thus, Rb₂O and Cs₂The respective contents of O are preferably within the above ranges.

In the optical glass of the present embodiment, the upper limit of the content of MgO is preferably 5%, and more preferably 4%, 3%, 2.5%, 2%, 1.5%, and 1% in this order. The lower limit of the content of MgO is preferably 0%. The content of MgO may be 0%.

In the optical glass of the present embodiment, the upper limit of the content of CaO is preferably 5%, and more preferably 4%, 3%, 2.5%, 2%, 1.5%, and 1% in this order. The lower limit of the CaO content is preferably 0%. The content of CaO may be 0%.

In the optical glass of the present embodiment, the upper limit of the SrO content is preferably 5%, and more preferably 4%, 3%, 2.5%, 2%, 1.5%, 1%, 0.5%, and 0.1% in this order. The lower limit of the SrO content is preferably 0%. The SrO content may be 0%.

In the optical glass of the present embodiment, the upper limit of the content of BaO is preferably 5%, and more preferably 4%, 3%, 2.5%, 2%, 1.5%, 1%, 0.5%, and 0.1% in this order. Further, the lower limit of the content of BaO is preferably 0%. The content of BaO may be 0%.

MgO, CaO, SrO and BaO are glass components having an effect of improving the meltability of the glass. However, when the content of these glass components is increased, the thermal stability of the glass is lowered and the glass is easily devitrified. Therefore, the content of each of these glass components is preferably within the above range.

In the optical glass of the present embodiment, the upper limit of the total content [ MgO + CaO + SrO + BaO ] of MgO, CaO, SrO and BaO is preferably 5%, and more preferably 4%, 3%, 2.5%, 2%, 1.5%, 1% in this order. The lower limit of the total content [ MgO + CaO + SrO + BaO ] is preferably 0%. The total content [ MgO + CaO + SrO + BaO ] may be 0%.

The total content [ MgO + CaO + SrO + BaO ] is preferably in the above range from the viewpoint of maintaining the thermal stability of the glass.

In the optical glass of the present embodiment, B₂O₃、SiO₂、Al₂O₃、La₂O₃、Gd₂O₃、Y₂O₃、ZnO、Li₂O、ZrO₂And Nb₂O₅Total content of [ B ]₂O₃+SiO₂+Al₂O₃+La₂O₃+Gd₂O₃+Y₂O₃+ZnO+Li₂O+ZrO₂+Nb₂O₅]The upper limit of (B) is preferably 100%. Further, the total content [ B ]₂O₃+SiO₂+Al₂O₃+La₂O₃+Gd₂O₃+Y₂O₃+ZnO+Li₂O+ZrO₂+Nb₂O₅]The lower limit of (b) is preferably 79%, and more preferably 80%, 82%, 84%, 86%, 88% in this order.

In this embodiment, B₂O₃、SiO₂And Al₂O₃Is a network forming component of glass, La₂O₃、Gd₂O₃And Y₂O₃ZnO and Li as glass components for increasing the refractive index without significantly reducing the Abbe number₂O is a glass having a refractive index not greatly loweredGlass component having an effect of lowering the transition temperature Tg, and ZrO₂And Nb₂O₅A glass component having the effect of increasing the refractive index of the glass and improving the thermal stability of the glass. Therefore, the total content [ B ]₂O₃+SiO₂+Al₂O₃+La₂O₃+Gd₂O₃+Y₂O₃+ZnO+Li₂O+ZrO₂+Nb₂O₅]Preferably within the above range.

In the optical glass of the present embodiment, Ga₂O₃The upper limit of the content of (b) is preferably 5%, and more preferably 4%, 3%, 2.5%, 2%, 1.5%, 1%, 0.5%, 0.1% in this order. Furthermore, Ga₂O₃The lower limit of the content of (b) is preferably 0%. In addition, Ga₂O₃The content of (B) may be 0%.

In the optical glass of the present embodiment, In₂O₃The upper limit of the content of (b) is preferably 5%, and more preferably 4%, 3%, 2.5%, 2%, 1.5%, 1%, 0.5%, 0.1% in this order. In addition, In₂O₃The lower limit of the content of (b) is preferably 0%. In addition, In₂O₃The content of (B) may be 0%.

In the optical glass of the present embodiment, Sc₂O₃The upper limit of the content of (b) is preferably 5%, and more preferably 4%, 3%, 2.5%, 2%, 1.5%, 1%, 0.5%, 0.1% in this order. Further, Sc₂O₃The lower limit of the content of (b) is preferably 0%. In addition, Sc₂O₃The content of (B) may be 0%.

In the optical glass of the present embodiment, HfO₂The upper limit of the content of (b) is preferably 5%, and more preferably 4%, 3%, 2.5%, 2%, 1.5%, 1%, 0.5%, 0.1% in this order. Further, HfO₂The lower limit of the content of (b) is preferably 0%. Further, HfO₂The content of (B) may be 0%.

Ga₂O₃、In₂O₃、Sc₂O₃、HfO₂Both have the effect of increasing the refractive index nd. However, these glass components are expensive and are not necessary for achieving the object of the invention. Therefore, Ga is preferred₂O₃、In₂O₃、Sc₂O₃、HfO₂The respective contents of (a) and (b) are within the above ranges.

In the optical glass of the present embodiment, Lu₂O₃The upper limit of the content of (b) is preferably 5%, and more preferably 4%, 3%, 2.5%, 2%, 1.5%, 1%, 0.5%, 0.1% in this order. Furthermore, Lu₂O₃The lower limit of the content of (b) is preferably 0%. In addition, Lu₂O₃The content of (B) may be 0%.

Lu₂O₃Has the effect of increasing the refractive index nd, but is compatible with Yb₂O₃Also, since it has a large molecular weight, it is a glass component which increases the specific gravity of the glass. Therefore, it is preferable to reduce Lu₂O₃Content of (1), Lu₂O₃The content of (b) is preferably in the above range.

In the optical glass of the present embodiment, GeO₂The upper limit of the content of (b) is preferably 3%, and more preferably 2%, 1%, 0.5%, and 0.1% in this order. Furthermore, GeO₂The lower limit of the content of (b) is preferably 0%. In addition, GeO₂The content of (B) may be 0%.

GeO₂Has the effect of increasing the refractive index nd, but is a particularly expensive component among the glass components generally used. Therefore, GeO is a useful material for reducing the production cost of glass₂The content of (b) is preferably in the above range.

In the optical glass of the present embodiment, P is₂O₅The upper limit of the content of (b) is preferably 5%, and more preferably 4%, 3%, 2%, 1%, 0.5%, 0.1% in this order. Furthermore, P₂O₅The lower limit of the content of (b) is preferably 0%. In addition, P₂O₅The content of (B) may be 0%.

P₂O₅The glass component is a component that lowers the refractive index nd, and is a component that lowers the thermal stability of the glass. P is a group of compounds having desired optical properties and excellent thermal stability₂O₅The content of (b) is preferably in the above range.

The optical glass of the present embodiment is preferably composed mainly of the above-mentioned glass components, that is, preferably composed of B₂O₃、SiO₂、Al₂O₃、La₂O₃、Gd₂O₃、Y₂O₃、Yb₂O₃、LaF₃、GdF₃、YF₃、YbF₃、ZnO、Li₂O、ZrO₂、Nb₂O₅、Ta₂O₅、WO₃、TiO₂、Bi₂O₃、Na₂O、K₂O、Rb₂O、Cs₂O、MgO、CaO、SrO、BaO、Ga₂O₃、In₂O₃、Sc₂O₃、HfO₂、Lu₂O₃、Yb₂O₃、GeO₂And P₂O₅The total content of the glass components is preferably more than 95%, more preferably more than 98%, still more preferably more than 99%, and still more preferably more than 99.5%.

In the optical glass of the present embodiment, TeO₂The upper limit of the content of (b) is preferably 3%, and more preferably 2%, 1%, 0.5%, and 0.1% in this order. Furthermore, TeO₂The lower limit of the content of (b) is preferably 0%. In addition, TeO₂The content of (B) may be 0%.

TeO₂Since the component having the refractive index nd is high but toxic, it is preferable to decrease TeO₂The content of (a). Thus, TeO₂The content of (b) is preferably in the above range.

In the optical glass of the present embodiment, when a halide is contained as a glass component, for example, LaF₃、GdF₃、YF₃、YbF₃That is, the compound contains a cation and a halide (anion).

A part of the halide ions introduced into the molten glass are replaced with oxygen ions which are also anions and are dissolved in a large amount in the molten glass. F substituted by oxygen ions^-、Cl^-、Br^-、I^-The halogen ions are all turned into gas and volatilized from the molten glass. Volatilization of halogen causes problems such as change in glass characteristics, deterioration in glass homogeneity, and significant consumption of melting equipment. Therefore, even when a halide is contained, it is preferable to reduce the content thereof.

For the above reasons, even when a halide is contained as a glass component, it is preferable to limit the content of the halide to a small amount so that the proportion (mass ratio) of the oxide in the entire glass component is not 95 mass% or less.

That is, in the optical glass of the present embodiment, the content of the oxide in the entire glass component is preferably more than 95 mass%. Further, the lower limit of the content of the oxide in the entire glass component is more preferably 97 mass%, 99 mass%, 99.5 mass%, 99.9 mass%, 99.95 mass%, 99.99 mass% in this order, and the content of the oxide in the entire glass component may be 100 mass%. The glass in which the content of the oxide in the entire glass components is 100 mass% does not substantially contain a halide.

The optical glass of the present embodiment is preferably substantially composed of the above glass components, but may contain other components within a range not to impair the action and effect of the present invention. In the present invention, the inclusion of inevitable impurities is not excluded.

< other component compositions >

Pb, As, Cd, Tl, Be, Se are toxic. Therefore, the optical glass of the present embodiment preferably does not contain these elements as glass components.

U, Th and Ra are radioactive elements. Therefore, the optical glass of the present embodiment preferably does not contain these elements as glass components.

V, Cr, Mn, Fe, Co, Ni, Cu, Pr, Nd, Pm, Sm, Eu, Tb, Dy, Ho, Er, Tm, and Ce increase the coloration of the glass and may be a source of fluorescence. Therefore, the optical glass of the present embodiment preferably does not contain these elements as glass components.

Sb(Sb₂O₃)、Sn(SnO₂)、Ce(CeO₂) Optionally added elements to function as fining agents. Wherein Sb (Sb)₂O₃) The clarifying agent has a large clarifying effect. However, Sb (Sb)₂O₃) If Sb (Sb) is used, the oxidizing property of the composition is strong₂O₃) Increase in the amount of Sb (Sb) contained in the glass during precision press molding₂O₃) The molding surface of the press molding die is oxidized. Therefore, the molding surface is significantly deteriorated in the process of repeating the precision press molding, and the precision press molding becomes impossible. In addition, the surface quality of the molded optical element may be reduced. And Sb (Sb)₂O₃) In contrast, Sn (SnO)₂)、Ce(CeO₂) Has a small clarification effect. When a large amount of Ce (CeO) is added₂) In time, the coloration of the glass becomes strong. Therefore, when a clarifier is added, it is preferable to add Sb (Sb)₂O₃) While paying attention to the amount added.

Sb₂O₃The content of (b) is expressed in an additive manner. Namely, mixing Sb₂O₃、SnO₂And CeO₂Sb content of all glass components except for 100 mass%₂O₃The content of (b) is preferably less than 1% by mass, more preferably less than 0.5% by mass, and still more preferably less than 0.1% by mass. Sb₂O₃The content of (b) may be 0 mass%.

SnO₂The content of (b) is also expressed in an additive manner. Namely, SnO₂、Sb₂O₃And CeO₂SnO when total content of all other glass components is 100% by mass₂The content of (b) is preferably less than 2% by mass, more preferably less than 1% by mass, even more preferably less than 0.5% by mass, and even more preferably less than 0.1% by mass. SnO₂The content of (b) may be 0 mass%. By adding SnO₂The content of (b) is in the above range, whereby the glass can be improved in the fining property.

CeO₂The content of (b) is also expressed in an additive manner. Namely, CeO is added₂、Sb₂O₃、SnO₂CeO in the case where the total content of all other glass components is 100 mass%₂The content of (b) is preferably less than 2% by mass, more preferably less than 1% by mass, even more preferably less than 0.5% by mass, and even more preferably less than 0.1% by mass. CeO (CeO)₂The content of (b) may be 0 mass%. By mixing CeO₂The content of (b) is in the above range, whereby the glass can be improved in the fining property.

The optical glass of the embodiment of the present invention has a large refractive index nd and an Abbe's number ν d, is homogeneous, is less colored, and has a low glass transition temperature Tg, and therefore is suitable as an optical glass for precision press molding.

The glass composition of the optical glass according to the embodiment of the present invention can be quantified by, for example, ICP-AES (Inductively Coupled Plasma-Atomic Emission Spectrometry) or a method such as ICP-MS (Inductively Coupled Plasma-Mass Spectrometry) as appropriate. The analytical value obtained by ICP-AES may contain a measurement error of about. + -. 5% of the analytical value, for example. In the present specification and the present invention, the content of the constituent component of the glass being 0% or not means that the constituent component is not substantially contained, and means that the content of the constituent component is not more than the impurity level.

(glass Properties)

< glass transition temperature Tg >

The upper limit of the glass transition temperature Tg of the optical glass of the present embodiment is preferably 630 ℃, and more preferably 625 ℃, 620 ℃, 615 ℃, 610 ℃, 605 ℃ and 600 ℃ in this order. The lower limit of the glass transition temperature Tg is preferably 570 ℃.

By making the upper limit of the glass transition temperature Tg within the above range, high precision press molding can be performed without excessively raising the temperature of the glass or press mold during precision press molding. As a result, the consumption of the press mold can be reduced, and the life of the press mold can be extended. Further, by lowering the glass transition temperature Tg, the reaction between the glass and the molding surface of the press mold during precision press molding can be suppressed, the shape accuracy of the surface of the optical element obtained by press molding can be improved, and the transparency of the surface can be improved.

< light transmittance of glass >

In the present embodiment, the light transmittance can be evaluated by the coloring degrees λ 5 and λ 80.

A glass (thickness of 10.0 mm. + -. 0.1mm) having 2 mutually parallel optically polished planes is used, and light is made to perpendicularly enter the plane from one of the above 2 planes. Then, the ratio (Iout/Iin) of the intensity Iout of the transmitted light emitted from the other plane to the intensity Iin of the incident light, that is, the external transmittance is calculated. The spectral transmittance curve is obtained by measuring the external transmittance while scanning the wavelength of incident light in the range of, for example, 280 to 700nm using a spectrophotometer.

The external transmittance increases as the wavelength of incident light shifts from the absorption edge on the short wavelength side of the glass to the long wavelength side, showing a high value.

λ 5 is a wavelength at which the external transmittance becomes 5%, and λ 80 is a wavelength at which the external transmittance becomes 80%. The external transmittance of the glass at the long wavelength side of lambda 5 shows a value of more than 5% in the wavelength region of 280 to 700 nm. Further, in the above wavelength region, the external transmittance of the glass at the long wavelength side of λ 80 shows a value larger than 80%.

By using optical glass with a reduced wavelength of λ 80, an optical element capable of reproducing a desired color can be provided. Further, by using the optical glass with a wavelength of λ 5 shortened, when the optical element produced is bonded using an ultraviolet-curable adhesive, it is possible to sufficiently ensure the transmission amount of ultraviolet light of the glass (the amount necessary for curing the adhesive), improve the bonding strength, and shorten the irradiation time of ultraviolet light.

For this reason, the λ 80 range is preferably 450nm or less, more preferably 445nm or less, and still more preferably 440nm or less. The lower limit of λ 80 is targeted at 370 nm. The λ 5 range is preferably 360nm or less, and more preferably 350nm or less. The lower limit of λ 5 is targeted at 200 nm.

< specific gravity of glass >

The optical glass of the present embodiment is a high refractive index low dispersion glass and has a small specific gravity. In general, if the specific gravity of glass can be reduced, the weight of the glass can be reduced. As a result, power consumption of the auto-focus drive of the camera lens having the lens mounted thereon can be reduced. On the other hand, if the specific gravity is excessively reduced, the refractive index nd and the thermal stability are lowered. Therefore, the upper limit of the specific gravity d is preferably 5.20, and more preferably 5.10, 5.08, and 5.05 in this order. From the viewpoint of increasing the refractive index and improving the thermal stability, the lower limit of the specific gravity d is preferably 4.2, and more preferably 4.3, 4.4, and 4.5 in this order.

< liquidus temperature >

The upper limit of the liquidus temperature of the optical glass of the present embodiment is preferably 1200 ℃, and more preferably 1180 ℃, 1170 ℃, 1160 ℃, 1150 ℃ in this order. The lower limit of the liquidus temperature is preferably 970 ℃, and more preferably 980 ℃, 1000 ℃, 1030 ℃ and 1050 ℃ in this order. According to the optical glass of the present embodiment, since the thermal stability of the glass can be improved, a high-refractive-index low-dispersion glass having a low glass transition temperature Tg can be obtained while reducing the content of Ta.

(production of optical glass)

The optical glass according to the embodiment of the present invention may be produced by preparing a glass raw material so as to have the above-described predetermined composition and producing the prepared glass raw material according to a known glass production method. For example, a plurality of compounds are prepared and mixed well to prepare a batch raw material, and the batch raw material is put into a platinum crucible to be roughly melted (rough melt). The melt obtained by the rough melting is quenched and pulverized to produce cullet. The cullet is placed in a platinum crucible and heated and remelted (remelt) to produce molten glass, and the molten glass is clarified and homogenized, and then molded and slowly cooled to obtain optical glass. The molten glass may be molded or gradually cooled by a known method.

The compound used in preparing the batch raw materials is not particularly limited as long as the desired glass component can be introduced into the glass in a desired content, and examples of such a compound include oxides, carbonates, nitrates, hydroxides, fluorides, and the like.

(production of optical element, etc.)

When the optical glass according to the embodiment of the present invention is used to manufacture an optical element, a known method may be applied. For example, a glass material made of the optical glass of the present invention is produced by melting a glass raw material to produce a molten glass, and pouring the molten glass into a mold to mold the molten glass into a plate shape. Then, the plate-like glass material is divided into several portions by a predetermined volume, and the glass surface is polished to produce a glass material for precision press molding (preform for precision press molding).

Alternatively, a molten glass is dropped and the dropped molten glass is formed into a droplet to produce a glass material for precision press molding (preform for precision press molding).

Then, these preforms for precision press molding are heated and precision press molded to produce optical elements. After the precision press molding, the processing such as centering and edging may be performed as necessary.

The optically functional surface of the optical element produced may be coated with an antireflection film, a total reflection film, or the like depending on the purpose of use.

Examples of the optical element include various lenses such as an aspherical lens, a microlens, and a lens array, and a diffraction grating.

Embodiment 2

(composition in cationic%)

In this embodiment (embodiment 2), as a 2 nd aspect of the present invention, an optical glass of the present invention will be described based on the content of each component expressed as cation%. Therefore, unless otherwise specified below, each content is expressed as cation%.

In the present specification, the term "cation%" means the content of each glass component expressed as cations, wherein the total content of all the cation components is 100% in terms of molar percentage. The total content is the total amount of the plurality of cationic components (including the case where the content is 0%). The cation ratio is a ratio of contents of the cation components expressed as cation% (including a total content of the plurality of cation components).

In addition, the valence number of the cationic component (e.g., B)³⁺Has a valence of +3, Si⁴⁺Has a valence of +4, La³⁺Valence of +3, Nb⁵⁺Valence of +5, Ti⁴⁺Has a valence of +4, W⁶⁺The valence of +6) is determined according to a value customary in the art to which the present invention pertains. In this field, the glass components B, Si, La, Nb, Ti and W are represented by oxides and B is represented by₂O₃、SiO₂、La₂O₃、Nb₂O₅、TiO₂、WO₃Is also based onAs determined by conventional notation in the art. Therefore, when the glass composition is analyzed, the valence number of the cation component may not be analyzed. In addition, the valence number (e.g., O) of the anionic component^2-The valence of (2) is determined according to a conventional value as well as the valence of the cationic component, and the glass component is represented as, for example, an oxide B as described above₂O₃、SiO₂、La₂O₃The same is true. Therefore, when analyzing the glass composition, the valence of the anion component may not be analyzed.

In addition, since the action and effect of each glass component in embodiment 2 are the same as those of each glass component in embodiment 1, the following description will be given centering on the numerical ranges (including preferable ranges) of the content, total content, and cation ratio of each component for the matters overlapping with the description of embodiment 1, and the overlapping matters are appropriately omitted.

The optical glass of the present embodiment is an oxide glass in which,

the ratio [ RE2/NWF2] of RE2 to NWF2 is 0.35 or more,

the ratio [ HR2/RE2] of HR2 to RE2 is 0.33 or less,

the ratio [ RE2/D2] of RE2 to D2 is 0.90 or more,

an Abbe number ν d of 39.0 or more and 45.0 or less, a refractive index nd satisfying the following formula (1),

nd≥2.235-0.01×νd···(1)

wherein,

NWF2 is B³⁺、Si⁴⁺And Al³⁺The total content of (a) to (b),

RE2 is La³⁺、Gd³⁺、Y³⁺And Yb³⁺The total content of (a) to (b),

HR2 is Nb⁵⁺、Ti⁴⁺、W⁶⁺And Bi³⁺The total content of (a) to (b),

D2＝(Li⁺+Na⁺+K⁺)×6+Zn²⁺，

the content of each component is a value expressed as cation%.

In the above formula, B represents³⁺、Si⁴⁺、Al³⁺、La³⁺、Gd³⁺、Y³⁺、Yb³⁺、Nb⁵⁺、Ti⁴⁺、W⁶⁺、Bi³⁺、Li⁺、Na⁺、K⁺、Zn⁺、Mg²⁺、Ca²⁺、Sr²⁺、Ba²⁺、Ta⁵⁺、Zr⁴⁺And La³⁺The content of each component (c) is the content of each component expressed in cationic%. L2 and D2 are indices of the content of a specific glass component in the optical glass of the present invention, and are expressed by numerical values alone, and do not add cation% or%. The same applies to the following description.

The optical glass of the present embodiment has an abbe number ν d of 39.0 or more and 45.0 or less, and the refractive index nd and the abbe number ν d satisfy the following formula (1).

nd≥2.235-0.01×νd···(1)

In the optical glass of the present embodiment, the abbe number ν d is 39.0 or more and 45.0 or less, and the lower limit of the abbe number ν d is preferably 39.5, more preferably 40.0, and further preferably 40.5. The upper limit of the abbe number ν d is preferably 44.5, more preferably 44.0, and further preferably 43.5.

In the optical glass of the present embodiment, the NWF2, RE2 and HR2 mean the total content of specific cations in terms of cation% per 100g of glass.

In the optical glass of the present embodiment, NWF2 is the network-forming component B expressed as cation%³⁺、Si⁴⁺And Al³⁺The total content of (NWF2 ═ B)³⁺+Si⁴⁺+Al³⁺)。

In the optical glass of the present embodiment, RE2 is a high-refractive-index low-dispersion component La represented by cation%³⁺、Gd³⁺、Y³⁺And Yb³⁺The total content of (RE2 ═ La) of³⁺+Gd³⁺+Y³⁺+Yb³⁺)。

In the optical glass of the present embodiment, the ratio of RE2 to NWF2, i.e., the cation ratio [ RE2/NWF2] is 0.35 or more.

In the optical glass of the present embodiment, the lower limit of the cation ratio [ RE2/NWF2] is preferably 0.40. The upper limit of the cation ratio [ RE2/NWF2] is preferably 0.55.

In the optical glass of the present embodiment, the upper limit of NWF2 is preferably 0.74, more preferably 0.72, even more preferably 0.70, and even more preferably 0.69. The lower limit of NWF2 is preferably 0.45, more preferably 0.48, still more preferably 0.50, and yet still more preferably 0.51.

In the optical glass of the present embodiment, the upper limit of RE2 is preferably 31, more preferably 29, still more preferably 28, and yet more preferably 27. The lower limit of RE2 is preferably 19, more preferably 21, still more preferably 22, and yet more preferably 23.

In the optical glass of the present embodiment, HR2 is a high-refractive-index high-dispersion component Nb represented by cation%⁵ ⁺、Ti⁴⁺、W⁶⁺And Bi³⁺The total content of (HR2 ═ Nb)⁵⁺+Ti⁴⁺+W⁶⁺+Bi³⁺)。

In the optical glass of the present embodiment, the ratio of HR2 to RE2, i.e., the cation ratio [ HR2/RE2] is 0.33 or less.

In the optical glass of the present embodiment, the upper limit of the cation ratio [ HR2/RE2] is preferably 0.32, and more preferably 0.31, 0.30, 0.29, 0.28, 0.27, and 0.25 in this order. The lower limit of the cation ratio [ HR2/RE2] is preferably 0.04, and more preferably 0.08, 0.10, 0.11, 0.13, 0.15, and 0.16 in this order.

The cation ratio [ HR2/RE2] is preferably in the above range from the viewpoint of achieving a desired refractive index and abbe number and providing an optical glass suitable for precision press molding.

In the optical glass of the present embodiment, the upper limit of HR2 is preferably 9, and more preferably 8.0, 7.5, 7.0, 6.5, and 6.0 in this order. The lower limit of HR2 is preferably 1, and more preferably 2.0, 2.5, 3.0, 3.5, and 4.0 in this order.

<Nb⁵⁺/(Nb⁵⁺+Ta⁵⁺)>

In the optical glass of the present embodiment, Nb⁵⁺Relative to the content of Nb⁵⁺And Ta⁵⁺The ratio of the total content of (a) to (b), i.e., the cation ratio [ Nb⁵⁺/(Nb⁵⁺+Ta⁵⁺)]Is above 3/4.

In the optical glass of the present embodiment, the cation ratio [ Nb ]⁵⁺/(Nb⁵⁺+Ta⁵⁺)]The lower limit of (b) is preferably 0.76, and more preferably 0.78, 0.80, 0.85, 0.90, 0.95, 0.97, 0.99, 1 in this order. Further, cation ratio [ Nb ]⁵⁺/(Nb⁵⁺+Ta⁵ ⁺)]The upper limit of (b) is preferably 1. In addition, cation ratio [ Nb ]⁵⁺/(Nb⁵⁺+Ta⁵⁺)]And may be 1.

In the optical glass of the present embodiment, D2 is Li which is more easily volatilized in terms of cation%⁺、Na⁺And K⁺The value of each content of (A) multiplied by 6 and volatile Zn in cation%²⁺The total value of the contents of (1) (D2 ═ Li⁺×6)+(Na⁺×6)+(K⁺×6)+Zn²⁺). That is, D2 can be expressed as D2 ═ Li (Li)⁺+Na⁺+K⁺)×6+Zn²⁺. D2 is an index for the content of volatile components in the optical glass of the present invention and is represented by numerical values only.

D2 is a numerical value of a factor that promotes volatilization during glass melting, and RE2 is a numerical value of a factor that suppresses volatilization during glass melting. That is, the ratio [ RE2/D2] is an index indicating the volatility of the glass melt.

Therefore, in the optical glass of the present embodiment, the ratio [ RE2/D2] is 0.90 or more.

In the optical glass of the present embodiment, the lower limit of the ratio [ RE2/D2] is preferably 0.95, and more preferably 1.00, 1.05, 1.10, 1.15, and 1.20 in this order. The upper limit of the ratio [ RE2/D2] is preferably 5, and more preferably 4, 3, 2.7, 2.5, and 2.4 in this order.

By setting the ratio [ RE2/D2] to 0.90 or more, volatilization of the molten glass, which is molten glass, can be suppressed. As a result, optical glass having desired characteristics can be stably produced. Further, high homogeneity of the glass can be maintained. On the other hand, by setting the upper limit of the ratio [ RE2/D2] to 5, the meltability of the glass can be improved, and the increase in the glass transition temperature Tg can be suppressed, so that a high-quality glass optical element can be stably produced by precision press molding.

The glass component is roughly divided into a component having an action of relatively lowering the glass transition temperature Tg and a component having an action of relatively raising the glass transition temperature Tg. The component having the effect of relatively lowering the glass transition temperature Tg is mainly Li⁺、Na⁺、K⁺、Zn²⁺、Mg²⁺、Ca²⁺、Sr²⁺、Ba²⁺、B³⁺、Nb⁵⁺、Ti⁴⁺、W⁶⁺、Bi³⁺、Ta⁵⁺. On the other hand, the component having the effect of relatively increasing the glass transition temperature Tg with respect to the glass component is mainly Si⁴⁺、Al³⁺、Zr⁴⁺、La³⁺、Gd³⁺、Y³⁺、Yb³⁺。

As a result of studies conducted by the inventors of the present application, it was found that there is a correlation between the ratio [ L2/(NWF2+ RE2) ] of L2 to the total value of NWF2 and RE2 and the glass transition temperature Tg, where L2 is the total value of values obtained by multiplying the values of the contents of the above-mentioned components expressed in cation% by the values of the influence of the components on the glass transition temperature Tg, respectively, as coefficients. Table 4 shows coefficients showing the influence of the above components on the glass transition temperature Tg based on the cation ratio.

[ Table 4]

Glass composition	Coefficient of performance	Glass composition	Coefficient of performance	Glass composition	Coefficient of performance
						Li⁺	+10	Ba²⁺	+2	Bi³⁺	+4
Na⁺	+8	B³⁺	+1	Ta⁵⁺	+1
						K⁺	+4	Si⁴⁺	-2	Zr⁴⁺	-2
Zn²⁺	+4	Al³⁺	-1	La³⁺	-1
						Mg²⁺	+1	Nb⁵⁺	+1	Gd³⁺	-1
Ca²⁺	+2	Ti⁴⁺	+1	Y³⁺	-1
						Sr²⁺	+2	W⁶⁺	+4	Yb³⁺	-1

Such an L2 can be represented as

L2＝(10×Li⁺)+(8×Na⁺)+(4×K⁺)+(4×Zn⁺)+(1×Mg²⁺)+(2×Ca²⁺)+(2×Sr²⁺)+(2×Ba²⁺)+(1×B³⁺)+(1×Nb⁵⁺)+(1×Ti⁴⁺)+(4×W⁶⁺)+(4×Bi³⁺)+(1×Ta⁵⁺)+(-2×Si⁴⁺)+(-1×Al³⁺)+(-2×Zr⁴⁺)+(-1×La³⁺)+(-1×Gd³⁺)+(-1×Y³⁺)+(-1×Yb³⁺)。

That is, L2 can be expressed as

L2＝(10×Li⁺)+(8×Na⁺)+(4×K⁺)+(4×Zn⁺)+Mg²⁺+(2×Ca²⁺)+(2×Sr²⁺)+(2×Ba² ⁺)+B³⁺+Nb⁵⁺+Ti⁴⁺+(4×W⁶⁺)+(4×Bi³⁺)+Ta⁵⁺-(2×Si⁴⁺)-Al³⁺-(2×Zr⁴⁺)-La³⁺-Gd³⁺-Y³⁺-Yb³⁺。

Fig. 2 is a graph in which the horizontal axis represents the ratio of L2 to the total value of NWF2 and RE2 [ L2/(NWF2+ RE2) ], and the vertical axis represents the glass transition temperature Tg, and the ratio [ L2/(NWF2+ RE2) ] and the glass transition temperature Tg are plotted for a known glass, where NWF2 represents the total content of the network-forming components in the glass component, and RE2 represents the total content of rare-earth ions. As is clear from fig. 2, the points are substantially distributed on a straight line, and it is understood that the ratio [ L2/(NWF2+ RE2) ] has a correlation with the glass transition temperature Tg.

That is, the glass transition temperature Tg decreases with an increase in the ratio [ L2/(NWF2+ RE2) ], and increases with a decrease in the ratio [ L2/(NWF2+ RE2) ].

In this manner, by increasing the ratio [ L2/(NWF2+ RE2) ], the glass transition temperature Tg can be lowered, and a glass suitable for precision press molding, that is, a glass having low-temperature softening properties can be provided. Further, the ratio [ L2/(NWF2+ RE2) ] is increased, whereby the meltability of the glass can be improved. That is, the glass raw material does not remain as molten glass, and homogeneous glass can be provided.

In the optical glass of the present embodiment, the ratio [ L2/(NWF2+ RE2) ] is 0.78 or more.

In the optical glass of the present embodiment, the lower limit of the ratio [ L2/(NWF2+ RE2) ] is preferably 0.80, and more preferably 0.85, 0.90, 0.95, 1.00, and 1.05 in this order.

From the viewpoint of obtaining low-temperature softening properties suitable for precision press molding and improving the meltability of the glass, the lower limit of the ratio [ L2/(NWF2+ RE2) ] is preferably in the above range.

< glass composition >

Hereinafter, the glass composition will be described in detail. Unless otherwise specified, the contents of various glass components (glass components) and the like are expressed in terms of cation% or anion%. The optical glass of the present embodiment is an oxide glass, and the glass composition can be determined by determining the content ratio (content) of the cationic component.

In the optical glass of the present embodiment, B³⁺The upper limit of the content of (b) is preferably 65%, and more preferably 62%, 60%, 57%, 56%, and 55% in this order. In addition, B³⁺The lower limit of the content of (b) is preferably 40%, and more preferably 43%, 45%, 46%, 47%, and 48% in this order.

In the optical glass of the present embodiment, Si⁴⁺The upper limit of the content of (b) is preferably 10%, and more preferably 8%, 7%, 6%, and 5% in this order. Further, Si⁴⁺The lower limit of the content of (b) is preferably 0%. In addition, Si⁴⁺The content of (B) may be 0%.

In the optical glass of the present embodiment, Al³⁺The upper limit of the content of (b) is preferably 10%, and more preferably 7%, 5%, 4%, 3%, 2.5%, 2%, 1.5%, 1%, 0.5%, 0.1%, 0.05% in this order. Further, Al³⁺The lower limit of the content of (b) is preferably 0%. In addition, Al³⁺The content of (B) may be 0%.

In the optical glass of the present embodiment, B³⁺、Si⁴⁺And Al³⁺Total content of [ B ]³⁺+Si⁴⁺+Al³⁺]The upper limit of (b) is preferably 62, and more preferably 60, 58, 56, and 55 in this order. Total content [ B³⁺+Si⁴⁺+Al³⁺]The lower limit of (b) is preferably 40, and more preferably 43, 45, 46, and 48 in this order.

In the optical glass of the present embodiment, B³⁺Relative to B³⁺、Si⁴⁺And Al³⁺Total content of [ B ]³⁺+Si⁴⁺+Al³⁺]Ratio of (A) to (B), i.e. cation ratio [ B ]³⁺/(B³⁺+Si⁴⁺+Al³⁺)]The upper limit of (b) is preferably 1. Further, cation ratio [ B ]³⁺/(B³⁺+Si⁴⁺+Al³⁺)]The lower limit of (b) is preferably 0.70, and more preferably 0.75, 0.80, 0.85, 0.88, and 0.90 in this order. In addition, cation ratio [ B ]³⁺/(B³⁺+Si⁴⁺+Al³⁺)]And may be 1.

In the optical glass of the present embodiment, La³⁺、Gd³⁺、Y³⁺And Yb³⁺Total content of [ La ]³⁺+Gd³⁺+Y³⁺+Yb³⁺]The upper limit of (b) is preferably 35%, and more preferably 30%, 28%, and 27% in this order. Further, the total content [ La ]³⁺+Gd³⁺+Y³⁺+Yb³ ⁺]The lower limit of (b) is preferably 16%, and more preferably 18%, 20%, 21%, 22%, and 23% in this order.

In the optical glass of the present embodiment, La³⁺The upper limit of the content of (b) is preferably 27%, and more preferably 25%, 23%, 22%, 21%, 20%, and 19% in this order. Further, La³⁺The lower limit of the content of (b) is preferably 5%, and more preferably 8%, 9%, 10%, and 11% in this order.

In the optical glass of the present embodiment, Gd³⁺The upper limit of the content of (b) is preferably 22%, and more preferably 20%, 18%, 15%, 14%, 13% in this order. In addition, Gd³⁺The lower limit of the content of (b) is preferably 1%, and more preferably 2%, 3%, 4%, and 5% in this order.

In the optical glass of the present embodiment, Y is³⁺The upper limit of the content of (b) is preferably 15%, and more preferably 12%, 10%, 8%, 5%, 4%, and 3% in this order. Furthermore, Y³⁺The lower limit of the content of (b) is preferably 0%.

In the optical glass of the present embodiment, Yb³⁺The upper limit of the content of (b) is preferably 5%, and more preferably 4%, 3%, 2.5%, 2%, 1.5%, 1%, 0.5%, 0.3%, 0.2%, 0.1%, 0.05%, 0.01% in this order. In addition, Yb³⁺The lower limit of the content of (b) is preferably 0%. In addition, Yb³⁺The content of (B) may be 0%.

In the optical glass of the present embodiment, La³⁺Relative to La³⁺、Gd³⁺、Y³⁺And Yb³⁺Total content of [ La ]³⁺+Gd³⁺+Y³⁺+Yb³⁺]The ratio of (A) to (B), i.e. the cation ratio [ La³⁺/(La³⁺+Gd³⁺+Y³⁺+Yb³⁺)]The upper limit of (b) is preferably 0.99, and more preferably 0.97, 0.95, 0.93, 0.90, 0.85, 0.80, 0.77, 0.76, 0.75 in this order. Further, cation ratio [ La ]³⁺/(La³⁺+Gd³⁺+Y³⁺+Yb³⁺)]The lower limit of (b) is preferably 0.3, and more preferably 0.4, 0.45, 0.46, 0.47, and 0.48 in this order. By making the cation ratio [ La ] of³⁺/(La³⁺+Gd³⁺+Y³⁺+Yb³⁺)]Within the above range, the thermal stability and meltability can be improved.

In the optical glass of the present embodiment, La³⁺、Gd³⁺、Y³⁺And Yb³⁺Total content of [ La ]³⁺+Gd³⁺+Y³⁺+Yb³⁺]Relative to B³⁺、Si⁴⁺And Al³⁺Total content of [ B ]³⁺+Si⁴⁺+Al³⁺]The ratio of (A) to (B), i.e., [ (La) is a cation ratio³⁺+Gd³⁺+Y³⁺+Yb³⁺)/(B³⁺+Si⁴⁺+Al³⁺)]The upper limit of (b) is preferably 0.80, and more preferably 0.70, 0.60, 0.55, 0.52, 0.51 in this order. Further, cation ratio [ (La)³⁺+Gd³⁺+Y³⁺+Yb³⁺)/(B³⁺+Si⁴⁺+Al³⁺)]The lower limit of (b) is preferably 0.35, and more preferably 0.36, 0.37, 0.38, 0.39, 0.40, 0.41, 0.42, 0.43 in this order.

In the optical glass of the present embodiment, Zn²⁺The upper limit of the content of (b) is preferably 25%, and more preferably 22%, 20%, 18%, 17%, 16%, 15% in this order. Furthermore, Zn²⁺The lower limit of the content of (C) is preferably 5%, andand more preferably 8%, 9%, 10%, 11%, 12%.

In the optical glass of the present embodiment, Zr⁴⁺The upper limit of the content of (b) is preferably 9%, and more preferably 8%, 7%, 6%, 5%, 4.5%, 4% in this order. In addition, Zr⁴⁺The lower limit of the content of (b) is preferably 0%, and more preferably 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5% in this order.

In the optical glass of the present embodiment, Nb⁵⁺The upper limit of the content of (b) is preferably 9%, and more preferably 8%, 7%, 6%, 5%, 4.5%, 4% in this order. Further, Nb⁵⁺The lower limit of the content of (b) is preferably 0.1%, and more preferably 0.2%, 0.3%, 0.5%, 1%, 2% in this order.

In the optical glass of the present embodiment, Ta⁵⁺The upper limit of the content of (b) is preferably 3%, and more preferably 2.5%, 2%, 1.5%, 1%, 0.5%, 0.1%, 0.05% in this order. Further, Ta⁵⁺The lower limit of the content of (b) is preferably 0%. In addition, Ta⁵ ⁺The content of (B) may be 0%.

In the optical glass of the present embodiment, Nb⁵⁺、Ti⁴⁺、W⁶⁺And Bi³⁺Total content of [ Nb ]⁵⁺+Ti⁴⁺+W⁶⁺+Bi³⁺]The upper limit of (b) is preferably 10%, and more preferably 9.0%, 8.0%, 7.0%, 6.5%, 6.0%. Further, the total content [ Nb ]⁵⁺+Ti⁴⁺+W⁶⁺+Bi³⁺]The lower limit of (b) is preferably 0.1%, and more preferably 0.2%, 0.3%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%.

In the optical glass of the present embodiment, Ti⁴⁺、W⁶⁺And Bi³⁺Total content of [ Ti⁴⁺+W⁶⁺+Bi³⁺]The upper limit of (b) is preferably 6%, and more preferably 5.5%, 5%, 4.5%, 4% in this order. Further, the total content [ Ti⁴⁺+W⁶⁺+Bi³⁺]The lower limit of (b) is preferably 0%, and more preferably 0.05%, 0.1%, 0.5% in this order,1.0％、1.5％、2.0％。

In the optical glass of the present embodiment, W⁶⁺The upper limit of the content of (b) is preferably 6%, and more preferably 5% and 4% in this order. Further, W⁶⁺The lower limit of the content of (b) is preferably 0%, and more preferably 0.1%, 0.5%, 0.8%, 1%, 1.5% in this order. In addition, W⁶⁺The content of (B) may be 0%. In addition, to obtain W⁶⁺W may be added to the glass transition temperature Tg of the glass⁶⁺The content of (B) is set to 0.5% or more.

In the optical glass of the present embodiment, Ti⁴⁺The upper limit of the content of (b) is preferably 5%, and more preferably 4%, 3%, 2.5%, 2%, 1.5%, 1%, 0.5%, 0.1%, 0.05% in this order. Further, Ti⁴⁺The lower limit of the content of (b) is preferably 0%. In addition, Ti⁴⁺The content of (B) may be 0%.

In the optical glass of the present embodiment, Bi³⁺The upper limit of the content of (b) is preferably 5%, and more preferably 4%, 3%, 2.5%, 2%, 1.5%, 1%, 0.5%, 0.1%, 0.05% in this order. In addition, Bi³⁺The lower limit of the content of (b) is preferably 0%. In addition, Bi³⁺The content of (B) may be 0%.

In the optical glass of the present embodiment, Li⁺The upper limit of the content of (b) is preferably 10%, and more preferably 8%, 6%, 5%, 4%, 3%, 2.5% in this order. Furthermore, Li⁺The lower limit of the content of (b) is preferably 0%. In addition, Li⁺The content of (B) may be 0%.

In the optical glass of the present embodiment, Na⁺The upper limit of the content of (b) is preferably 5%, and more preferably 4%, 3%, 2.5%, 2%, 1.5%, 1%, 0.5%, 0.1%, 0.05% in this order. Further, Na⁺The lower limit of the content of (b) is preferably 0%. In addition, Na⁺The content of (B) may be 0%.

In the optical glass of the present embodiment, K⁺The upper limit of the content of (C) is preferably 5%, andand more preferably 4%, 3%, 2.5%, 2%, 1.5%, 1%, 0.5%, 0.1%, 0.05% in order. Furthermore, K⁺The lower limit of the content of (b) is preferably 0%. In addition, K⁺The content of (B) may be 0%.

In the optical glass of the present embodiment, Li⁺、Na⁺And K⁺Total content of [ Li ]⁺+Na⁺+K⁺]The upper limit of (b) is preferably 10%, and more preferably 8%, 6%, 5%, 4%, 3.5%, 3% in this order. Further, the total content [ Li⁺+Na⁺+K⁺]The lower limit of (B) is preferably 0%. Further, the total content [ Li⁺+Na⁺+K⁺]The concentration may be 0%.

In the optical glass of the present embodiment, Rb⁺The upper limit of the content of (b) is preferably 3%, and more preferably 2.5%, 2%, 1.5%, 1%, 0.5%, 0.1%, 0.05% in this order. In addition, Rb⁺The lower limit of the content of (b) is preferably 0%. In addition, Rb⁺The content of (B) may be 0%.

In the optical glass of the present embodiment, Cs⁺The upper limit of the content of (b) is preferably 3%, and more preferably 2.5%, 2%, 1.5%, 1%, 0.5%, 0.1%, 0.05% in this order. In addition, Cs⁺The lower limit of the content of (b) is preferably 0%. In addition, Cs⁺The content of (B) may be 0%.

In the optical glass of the present embodiment, Mg²⁺The upper limit of the content of (b) is preferably 10%, and more preferably 7%, 5%, 4%, 3%, 2%, 1.5%, 1%, 0.5%, 0.1% in this order. Further, Mg²⁺The lower limit of the content of (b) is preferably 0%. In addition, Mg²⁺The content of (B) may be 0%.

In the optical glass of the present embodiment, Ca²⁺The upper limit of the content of (b) is preferably 10%, and more preferably 7%, 5%, 4%, 3%, 2%, 1.5%, 1%, 0.5%, 0.1% in this order. Further, Ca²⁺The lower limit of the content of (b) is preferably 0%. In addition, Ca²⁺The content of (B) may be 0%.

In the optical glass of the present embodiment, Sr²⁺The upper limit of the content of (b) is preferably 10%, and more preferably 7%, 5%, 4%, 3%, 2%, 1.5%, 1%, 0.5%, 0.1% in this order. In addition, Sr²⁺The lower limit of the content of (b) is preferably 0%. In addition, Sr²⁺The content of (B) may be 0%.

In the optical glass of the present embodiment, Ba²⁺The upper limit of the content of (b) is preferably 10%, and more preferably 7%, 5%, 4%, 3%, 2%, 1.5%, 1%, 0.5%, 0.1% in this order. In addition, Ba²⁺The lower limit of the content of (b) is preferably 0%. In addition, Ba²⁺The content of (B) may be 0%.

In the optical glass of the present embodiment, Mg²⁺、Ca²⁺、Sr²⁺And Ba²⁺Total content of [ Mg ]²⁺+Ca²⁺+Sr²⁺+Ba² ⁺]The upper limit of (b) is preferably 10%, and more preferably 7%, 5%, 4%, 3%, 2%, 1.5%, 1%, 0.5%, 0.1% in this order. Further, the total content [ Mg²⁺+Ca²⁺+Sr²⁺+Ba²⁺]The lower limit of (B) is preferably 0%. Further, the total content [ Mg²⁺+Ca²⁺+Sr²⁺+Ba² ⁺]The concentration may be 0%.

In the optical glass of the present embodiment, Ga³⁺The upper limit of the content of (b) is preferably 5%, and more preferably 4%, 3%, 2.5%, 2%, 1.5%, 1%, 0.5%, 0.1%, 0.05% in this order. Furthermore, Ga³⁺The lower limit of the content of (b) is preferably 0%. In addition, Ga³⁺The content of (B) may be 0%.

In the optical glass of the present embodiment, In³⁺The upper limit of the content of (b) is preferably 5%, and more preferably 4%, 3%, 2.5%, 2%, 1.5%, 1%, 0.5%, 0.1%, 0.05% in this order. In addition, In³⁺The lower limit of the content of (b) is preferably 0%. In addition, In³⁺The content of (B) may be 0%.

In the optical glass of the present embodiment, Sc³⁺The upper limit of the content of (b) is preferably 5%, and more preferably 4%, 3%, 2.5%, 2%, 1.5%, 1%, 0.5%, 0.1%, 0.05% in this order. Further, Sc³⁺The lower limit of the content of (b) is preferably 0%. In addition, Sc³⁺The content of (B) may be 0%.

In the optical glass of the present embodiment, Hf is⁴⁺The upper limit of the content of (b) is preferably 5%, and more preferably 4%, 3%, 2.5%, 2%, 1.5%, 1%, 0.5%, 0.1%, 0.05% in this order. Furthermore, Hf⁴⁺The lower limit of the content of (b) is preferably 0%. In addition, Hf⁴⁺The content of (B) may be 0%.

In the optical glass of the present embodiment, Lu³⁺The upper limit of the content of (b) is preferably 5%, and more preferably 4%, 3%, 2.5%, 2%, 1.5%, 1%, 0.5%, 0.1%, 0.05% in this order. Furthermore, Lu³⁺The lower limit of the content of (b) is preferably 0%. In addition, Lu³⁺The content of (B) may be 0%.

In the optical glass of the present embodiment, Ge⁴⁺The upper limit of the content of (b) is preferably 5%, and more preferably 4%, 3%, 2.5%, 2%, 1.5%, 1%, 0.5%, 0.1%, 0.05% in this order. In addition, Ge⁴⁺The lower limit of the content of (b) is preferably 0%. In addition, Ge⁴⁺The content of (B) may be 0%.

In the optical glass of the present embodiment, P is⁵⁺The upper limit of the content of (b) is preferably 3%, and more preferably 2.5%, 2%, 1.5%, 1%, 0.5%, 0.1%, 0.05% in this order. Furthermore, P⁵⁺The lower limit of the content of (b) is preferably 0%. In addition, P⁵ ⁺The content of (B) may be 0%.

The cationic component of the optical glass of the present embodiment is preferably composed mainly of the above-mentioned components, that is, preferably B³⁺、Si⁴⁺、Al³⁺、La³⁺、Gd³⁺、Y³⁺、Yb³⁺、Zn²⁺、Zr⁴⁺、Nb⁵⁺、Ta⁵⁺、W⁶⁺、Ti⁴⁺、Bi³⁺、Li⁺、Na⁺、K⁺、Rb⁺、Cs⁺、Mg²⁺、Ca²⁺、Sr²⁺、Ba²⁺、Ga³⁺、In³⁺、Sc³⁺、Hf⁴⁺、Lu³⁺、Ge⁴⁺And P⁵⁺The total content of the above components is preferably more than 95%, more preferably more than 98%, still more preferably more than 99%, and still more preferably more than 99.5%.

In the optical glass of the present embodiment, Te⁴⁺The upper limit of the content of (b) is preferably 3%, and more preferably 2.5%, 2%, 1.5%, 1%, 0.5%, 0.1%, 0.05% in this order. Further, Te⁴⁺The lower limit of the content of (b) is preferably 0%. In addition, Te⁴ ⁺The content of (B) may be 0%.

The glass of the present invention is an oxide glass, and the main component of the anion component is O^2-. Anion component O^2-The content range of (b) is preferably more than 95% and 100% or less of anion%, more preferably more than 97% and 100% or less of anion%, still more preferably more than 99% and 100% or less of anion%, still more preferably more than 99.5% and 100% or less of anion%, still more preferably more than 99.9% and 100% or less of anion%, and still more preferably 100% of anion%.

The glass of the present invention may also contain O^2-Other anionic components. As O^2-Other anion component, F^-、Cl^-、Br^-、I^-. However, F^-、Cl^-、Br^-、I^-Are easily volatilized during the melting of the glass. Volatilization of these components causes problems such as change in glass characteristics, deterioration in glass homogeneity, and significant consumption of melting equipment. Thus, F^-、Cl^-、Br^-And I^-The total content of (A) is preferably less than 5 anionic%, more preferably less thanLess than 3 anions%, more preferably less than 1 anion%, still more preferably less than 0.5 anions%, still more preferably less than 0.1 anions%, and still more preferably 0 anions%.

The anion% refers to a molar percentage in which the total content of all anion components is 100%.

The optical glass of the present embodiment is preferably composed substantially of the above components, but may contain other components within a range not to impair the action and effect of the present invention. In addition, the inclusion of unavoidable impurities is not excluded in the present invention.

The other component composition in embodiment 2 can be the same as in embodiment 1. The glass characteristics, optical glass production, optical element production, and the like of embodiment 2 can be the same as those of embodiment 1.

The embodiments of the present invention have been described above, but the present invention is not limited to the embodiments and can be implemented in various ways within a range not departing from the gist of the present invention.

In the present specification, the glass composition of the optical glass is described in terms of mass% and cation%, but the respective expression methods can be converted into each other by a conversion method as described later, for example.

The result of quantitative analysis of the glass composition and the glass component may be expressed on an oxide basis, and the content of the glass component may be expressed in mass%. The expression of such a composition can be converted into a composition expressed in terms of cation% and anion% by the following method, for example.

The oxide composed of cation A and oxygen is represented as A_mO_n. m and n are integers determined according to the stoichiometry, respectively. For example, for B³⁺Expressed as B on an oxide basis₂O₃Where m is 2 and n is 3, for Si⁴⁺Then is SiO₂，m＝1，n＝2。

First, A will be expressed in mass%_mO_nIs divided by A_mO_nAnd then multiplied by m. This value is set to P. Then, the sum of P was determined for all glass components. When the sum of P is Σ P, the value obtained by normalizing the value of P in each glass component so that Σ P becomes 100% is a represented by cation%^s+The content of (a). Here, s is 2 n/m.

The content of each component in mass% may be calculated from the content of each component in cation%, and the procedure opposite to the above procedure may be performed.

Moreover, Σ P does not contain Sb that can be added in a small amount as a clarifying agent₂O₃、SnO₂、CeO₂. Then, Sb₂O₃、SnO₂、CeO₂The respective contents of (a) are defined as the contents to be added. The amounts added are as described above.

The molecular weights mentioned above are as described above.

[ examples ]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

(example 1)

Tables 5A to 7A and tables 5B to 7B show the glass compositions and their characteristic values of the optical glasses (samples 1 to 23) of the examples of the present invention.

Here, the glass compositions of samples 1 to 23 are shown in mass% in tables 5A to 7A, and the glass compositions of samples 1 to 23 are shown in cation% in tables 5B to 7B. That is, although the glass compositions are shown in tables 5A to 7A and tables 5B to 7B in different ways, the optical glasses having the same sample number mean the same optical glasses having the same compositions. Therefore, tables 5A to 7A and tables 5B to 7B show substantially the same optical glasses and the results thereof. The same applies to tables 8A and 8B and tables 9A and 9B described later.

In tables 5B to 9B, the glass compositions are represented by cation%, but the anion components are all O^2-. Namely, the compositions described in tables 5B to 9B, O^2-The contents of (A) are all 100 anion%.

The compositions in mass% in tables 5A to 9A are compositions obtained by converting the compositions in cation% in tables 5B to 9B.

Various evaluations were made on the optical glass produced by the following procedure. The results are shown in tables 5A to 7A and tables 5B to 7B.

< melting and Molding of optical glass >

Oxides, hydroxides, carbonates, and nitrates corresponding to the constituent components of the glass were prepared as raw materials, and the raw materials were weighed and blended so that the glass composition of the obtained optical glass was each composition shown in each table, and the raw materials were thoroughly mixed to prepare blended raw materials. The obtained formulated raw material (batch raw material) is put into a platinum crucible, and is put into an electric furnace set to 1250 to 1350 ℃ together with the crucible, and is stirred while being melted for 120 to 180 minutes to homogenize and defoam (clarify). Thereafter, the platinum crucible containing the molten glass was taken out of the electric furnace, and the molten glass was cast into the preheated mold by tilting the platinum crucible. The mold is preheated by being placed in an electric furnace set at a temperature near the glass transition temperature Tg for 5 to 10 minutes, and the mold is taken out of the electric furnace for use in casting molten glass. In order to prevent the shape of the cast glass from being deformed, the glass is allowed to stand in a mold for several seconds to several tens of seconds, then immediately transferred into a slow cooling furnace together with the mold, annealed in the slow cooling furnace set at a temperature near the glass transition temperature Tg for about 1 hour, and then slowly cooled to room temperature to obtain each optical glass. In addition, the preparation of the samples was all carried out in an atmospheric environment.

The obtained glass was found to have no foreign matter such as a molten residue of the raw material, crystal precipitation, and bubbles, and was confirmed to be an optical glass having high homogeneity.

< evaluation of optical glass >

The refractive index nd, Abbe number ν d, glass transition temperature Tg, λ 80, λ 5, and specific gravity of each of the obtained optical glasses were measured.

The refractive index nd, Abbe number ν d, glass transition temperature Tg, specific gravity, coloring degree λ 5, λ 80, and liquidus temperature were measured by the following methods.

(1) Confirmation of glass composition

The glass composition was determined by selecting appropriate amounts of the optical glasses obtained as described above and quantifying the content of each component by inductively coupled plasma atomic emission spectrometry (ICP-AES method), and it was confirmed that the glass compositions agreed with the oxide compositions of the samples shown in tables 5A to 7A and tables 5B to 7B.

(2) Refractive index nd, Abbe number vd

According to the refractive index measurement method standardized by the japan optical glass industry association, an optical glass that is slowly cooled to room temperature is cut so that a glass having a shape that can sufficiently anneal a sample (for example, a square shape of 40mm × 40mm or less and a thickness of 25mm or less) and a size sufficient for making a prism described later can be obtained. Then, the glass is heated to a temperature between the glass transition temperature Tg and (Tg +30 ℃) at a temperature raising rate (for example, 40 to 50 ℃/hour) at which the temperature of the glass can follow the temperature raising, and the glass is held for 90 to 180 minutes to remove the stress in the glass. Then, the glass was gradually cooled at a cooling rate of-30 ℃ C/hr. times.4 hr, and then left to cool to obtain an optical glass. The obtained optical glass was processed to prepare a prism, and refractive indices nd, nF, and nc were measured using a precision spectrometer GMR-1 (trade name) manufactured by Shimadzu instruments. Further, Abbe number ν d is calculated using the measured values of refractive indices nd, nF, and nc.

(3) Glass transition temperature Tg

The temperature was measured at a temperature rise rate of 4 ℃ per minute using a thermomechanical analyzer manufactured by chemical Corporation (Rigaku Corporation).

(4) Specific gravity of

The measurement was performed by the archimedes method.

(5) Coloring degree of lambda 5, lambda 80

A sample of glass having a thickness of 10 mm. + -. 0.1mm was measured for spectral transmittance using a spectrophotometer. λ 5 and λ 80 were calculated from the spectral transmittances.

(6) Liquidus temperature

Approximately 5cc (5ml) of glass was placed in a platinum crucible, heated at 1250 ℃ to 1350 ℃ for 15 minutes, and then cooled to a temperature lower than the glass transition temperature Tg. The cooled glass was moved into a furnace at a predetermined temperature and held for 2 hours, and then the lowest temperature at which no crystal deposition was observed was defined as the liquidus temperature. The presence or absence of crystal precipitation was visually confirmed by using an optical microscope with a magnification of 100 times.

[ Table 5A ]

[ Table 6A ]

[ Table 7A ]

[ Table 5B ]

[ Table 6B ]

[ Table 7B ]

(example 2)

Preforms for precision press molding were produced using the various optical glasses obtained in example 1. The preform is fabricated using known methods.

The preform is heated and softened in a nitrogen atmosphere, and precision press-molded with a press-molding die to mold the glass into an aspherical lens shape. The molded glass was taken out of the press mold and annealed to produce aspherical lenses made of the optical glasses produced in example 1.

No defects such as cloudiness (decreased transparency), bubbles, and scratches were observed on the surface of the aspherical lens thus produced.

Comparative example 1

In 5 compositions (samples 24 to 28) of examples 1, 4, 14, 19 and 21 of patent document 6 (jp 2009-. The mass of the melt was 200 g.

Tables 8A and 8B show the glass compositions and their characteristic values of samples 24 to 28. Since the compositions of samples 24 to 28 do not contain Nb, devitrification (crystal precipitation) occurs in all of them.

[ Table 8A ]

[ Table 8B ]

Comparative example 2

The glasses (samples 29 to 32) of examples 2 and 4, 8 and 15 of patent documents 3 (Japanese patent laid-open publication No. 2002-12443) and 7 (Japanese patent publication No. 2009-537427) were reproduced. The glass compositions and their characteristic values of samples 29 to 32 are shown in tables 9A and 9B. In the compositions of samples 29 to 32, the ratio RE1/D1 and the ratio RE2/D2, which are indicators of volatility, are both small, and the amount of volatilization of the glass in a molten state increases.

[ Table 9A ]

[ Table 9B ]

Samples (about 50mg) made of glasses of samples 29 to 32 were melted at 1200 ℃ for 1 hour, and the mass before and after the melting was measured to determine the mass loss amount and the mass loss rate. Table 10 shows the mass of samples 29 to 32 before melting, the mass loss amount due to melting, and the mass loss rate. The mass reduction caused by the melting of the sample is caused by the volatilization of the molten glass.

[ Table 10]

Further, the mass loss of the sample was measured by TG-DTA. On the other hand, the same experiment was carried out for each glass of the examples of the present application, and the mass reduction rate was 0.74% or less, which is a small value as 1/3 to 1/2 of the mass reduction rate of the glass of the above-mentioned samples 29 to 32.

Comparative example 3

The glass of example 4 (sample 30) of patent document 7 (japanese patent application publication No. 2009-537427) was held at 1200 ℃ for 2 hours, 4 hours, and 6 hours, respectively, and cooled to measure the refractive index nd, and the results shown in table 11 were obtained.

[ Table 11]

Retention time at 1200 deg.C	Refractive index nd	Amount of change in refractive index nd (Note)
			2 hours	1.79682	0
4 hours	1.79923	+0.00241
			6 hours	1.79991	+0.00309

(Note) the value of the refractive index nd at 1200 ℃ for 2 hours was used as a reference.

On the other hand, the change in refractive index nd of the glass of sample 16 in the present example is shown in Table 12.

[ Table 12]

Retention time at 1200 deg.C	Refractive index nd	Amount of change in refractive index nd (Note)
			2 hours	1.82102	0
4 hours	1.82138	+0.00036
			6 hours	1.82157	+0.00055

In the glasses of the examples of the present application other than sample 16, the absolute value of the difference between the refractive index nd after holding at 1200 ℃ for 2 hours and the refractive index nd after holding for 6 hours is also not less than 0.00070. In either case, since the component that is less volatile has a stronger effect of increasing the refractive index than the component that is volatile, the refractive index increases by increasing the holding time.

Thus, it is found that by increasing the ratio [ RE1/D1] and the ratio [ RE2/D2] which are indicators of volatility, the volatility can be reduced, and the amount of change in the refractive index nd can be reduced to 1/7 to 1/4.

Claims

1. An optical glass, wherein,

the ratio [ RE1/NWF1] of RE1 to NWF1 is 0.37 to 0.80,

the ratio [ HR1/RE1] of HR1 to RE1 is 0.33 or less,

B₂O₃the content of (B) is 15 to 32% by mass,

SiO₂the content of (B) is 0 to 7% by mass,

ZrO₂the content of (B) is 0.1 mass% or more,

the ratio [ RE1/D1] of RE1 to D1 is 0.90 or more,

an Abbe number vd of 39.0 or more and 44.5 or less, the Abbe number vd and a refractive index nd satisfying the following formula (1),

nd≥2.235-0.01×νd…(1)

wherein,

NWF1＝[2×B₂O₃/M(B₂O₃)]+[SiO₂/M(SiO₂)]+[2×Al₂O₃/M(Al₂O₃)]

the content of each glass component is a value expressed by mass%.

2. An optical glass which is an oxide glass, wherein,

the ratio [ RE2/NWF2] of RE2 to NWF2 is 0.40 to 0.55,

the ratio [ HR2/RE2] of HR2 to RE2 is 0.33 or less,

B³⁺the content of (A) is 40-65 cation%,

Si⁴⁺the content of (B) is 0-10 cation%,

Zr⁴⁺the content of (A) is more than 0.1 cation percent,

the ratio [ RE2/D2] of RE2 to D2 is 0.90 or more,

an Abbe number vd of 39.0 or more and 44.5 or less, the Abbe number vd and a refractive index nd satisfying the following formula (1):

nd≥2.235-0.01×νd…(1)

wherein,

NWF2 is B³⁺、Si⁴⁺And Al³⁺The total content of (a) to (b),

RE2 is La³⁺、Gd³⁺、Y³⁺And Yb³⁺The total content of (a) to (b),

HR2 is Nb⁵⁺、Ti⁴⁺、W⁶⁺And Bi³⁺The total content of (a) to (b),

D2＝(Li⁺+Na⁺+K⁺)×6+Zn²⁺，

L2＝(10×Li⁺)+(8×Na⁺)+(4×K⁺)+(4×Zn⁺)+Mg²⁺+(2×Ca²⁺)+(2×Sr²⁺)+(2×Ba²⁺)+B³⁺+Nb⁵⁺+Ti⁴⁺+(4×W⁶⁺)+(4×Bi³⁺)+Ta⁵⁺-(2×Si⁴⁺)-Al³⁺-(2×Zr⁴⁺)-La³⁺-Gd³⁺-Y³⁺-Yb³⁺，

the content of each glass component is a value expressed as cation%.

3. A preform for precision press molding, which comprises the optical glass according to claim 1 or 2.

4. An optical element comprising the optical glass according to claim 1 or 2.