JP7014588B2 - Optical glass and optical elements - Google Patents

Description

The present invention relates to optical glass and optical elements.

Patent Document 1 discloses an optical glass having a refractive index nd of 1.8 or more and an Abbe number νd of about 30.
The optical glass described in Patent Document 1 has devitrification stability when molding molten glass (glass melt) (devitrification resistance when the glass melt is vitrified) and heats the molded glass. Both are excellent in devitrification stability (devitrification resistance when reheating glass) when softened and remolded.

Japanese Unexamined Patent Publication No. 2007-254197

Generally, the partial dispersion ratios Pg and F of an optical glass having a refractive index nd near 1.8 and an Abbe number νd around 30 are shown on a graph in which the horizontal axis is the Abbe number νd and the vertical axis is the partial dispersion ratio Pg and F. , It is distributed along a linear reference line, which is generally called a normal line. Then, in the range where the Abbe number νd is smaller than about 30, the partial dispersion ratios Pg, F and the deviations ΔPg, F of the normal line take positive values, and in the range where the Abbe number νd is larger than about 30, the partial dispersion ratio Pg, Deviations ΔPg and F between F and the normal line take negative values (except for glasses with positive anomalous partial dispersibility such as futuric acid glass).

In the design of optical systems, the correction of primary chromatic aberration is performed by combining two types of glass with different Abbe numbers. The glass used for high-order chromatic aberration correction is selected in consideration of the Abbe number and the partial dispersion ratio.

In an optical glass having an Abbe number νd of about 30, a glass having a small partial dispersion ratio is suitable for high-order chromatic aberration correction.
Further, the optical element mounted on the autofocus type optical system is required to be lightweight in order to reduce the power consumption when driving the autofocus function, and glass having a relatively low specific density is suitable.

It is an object of the present invention to solve the above problems, to provide an optical glass having desired optical characteristics and a relatively small specific gravity, and to provide an optical element made of the optical glass.

The gist of the present invention is as follows.
(1) Containing SiO ₂ , Nb ₂ O ₅ , TIO ₂ , and CaO as essential components,
The mass ratio of the total content of Nb ₂ O ₅ and TIO ₂ to the total content of SiO ₂ and B ₂ O ₃ ((Nb ₂ O ₅ + TiO ₂ ) / (SiO ₂ + B ₂ O ₃ )) is 1.120 or more. ,
The mass ratio of the content of B ₂ O ₃ to the content of SiO ₂ (B ₂ O ₃ / SiO ₂ ) is less than 1.
Mass ratio of total content of SiO ₂ and B ₂ O ₃ to total content of SiO ₂ , B ₂ O ₃ and P ₂ O ₅ (SiO ₂ + B ₂ O ₃ ) / (SiO ₂ + B ₂ O ₃ + P ₂ O ₅ ) is 0.9 or more,
The mass ratio of BaO content to CaO content (BaO / CaO) is less than 1,
The mass ratio of the content of TiO ₂ to the total content of MgO, CaO, SrO and BaO (TiO ₂ / (MgO + CaO + SrO + BaO)) is 0.220 or more,
The content of Ta ₂ O ₅ is 2% by mass or less,
GeO ₂ content is 2% by mass or less,
Optical glass.

(2) The optical glass according to (1), wherein the total content of Nb ₂ O ₅ and TiO ₂ is 15 to 50% by mass.

(3) The optical glass according to (1) or (2), wherein the content of SiO ₂ is 10 to 40% by mass.

(4) The optical glass according to any one of (1) to (3), wherein the total content of the alkali metal oxide exceeds 0% by mass.

(5) An optical element made of the optical glass according to any one of (1) to (4) above.

According to one aspect of the present invention, it is possible to provide an optical glass having desired optical characteristics and a relatively small specific gravity, and to provide an optical element made of the optical glass.

Hereinafter, one aspect of the present invention will be described. In addition, in this invention and this specification, the glass composition of an optical glass is shown by an oxide standard unless otherwise specified. Here, the "oxide-based glass composition" refers to a glass composition obtained by converting all glass raw materials into those that are decomposed at the time of melting and exist as oxides in optical glass, and the notation of each glass component is According to the custom, SiO ₂ , TiO ₂ , etc. are described. Unless otherwise specified, the content and total content of glass components are based on mass, and "%" means "% by mass".

The content of the glass component can be quantified by a known method, for example, an inductively coupled plasma emission spectroscopic analysis method (ICP-AES), an inductively coupled plasma mass spectrometry method (ICP-MS), or the like. Further, in the present specification and the present invention, the content of the constituent component is 0%, which means that the constituent component is substantially not contained, and the component is allowed to be contained at an unavoidable impurity level.

One aspect of the present invention is an optical glass containing SiO ₂ , Nb ₂ O ₅ , TiO ₂ , and CaO as essential components.

SiO ₂ is a network forming component of glass and is an essential component.
Nb ₂ O ₅ and TiO ₂ have the functions of increasing the refractive index of glass and increasing the dispersion, and both are essential components for obtaining desired optical characteristics.

CaO is a component that maintains the thermal stability and meltability of glass and reduces dispersion. When Nb ₂ O ₅ and TiO ₂ are introduced, the refractive index increases, but the dispersion becomes high and the partial dispersion ratio increases. , The partial dispersion ratio can be reduced to obtain an optical glass suitable for high-order chromatic aberration correction. Further, CaO is a component that does not easily increase the specific gravity of glass, and is also an effective component for obtaining glass having a small specific gravity. The preferable range of the CaO content is more than 0% and 35% or less. The preferred upper limit of the CaO content is 33%, more preferably 31%, 30%, 29%, 28% and 27%. The preferred lower limit of the CaO content is 3%, further 4%, 5%, 6%, 6.5%, 7.5%, 8.1%, 12.5%, 13.4%. The order of 14.3%, 15.5%, and 16.0% is more preferable.

B ₂ O ₃ is an optional component that works together with SiO ₂ to form a glass network. However, the mass ratio of the total content of Nb ₂ O ₅ and TiO ₂ to the total content of SiO ₂ and B ₂ O ₃ ((Nb ₂ O ₅ + TiO ₂ ) / (SiO ₂ + B ₂ O ₃ )) is 1. If it is less than 120, the refractive index is lowered and it becomes difficult to obtain desired optical characteristics.

Therefore, the mass ratio ((Nb ₂ O ₅ + TiO ₂ ) / (SiO ₂ + B ₂ O ₃ )) is 1.120 or more in order to obtain desired optical characteristics. The preferable lower limit of the mass ratio ((Nb ₂ O ₅ + TiO ₂ ) / (SiO ₂ + B ₂ O ₃ )) is 1.122, and further, 1.124, 1.126, 1.128, 1.130, The order of 1.132, 1.134, 1.136, 1.138, 1.140 is more preferable.

On the other hand, if the mass ratio ((Nb ₂ O ₅ + TiO ₂ ) / (SiO ₂ + B ₂ O ₃ )) is too large, the Abbe number νd decreases, the partial dispersion ratio increases, and the devitrification resistance tends to decrease. Is shown. Therefore, in order to obtain an optical glass that is suitable for high-order chromatic aberration correction and has excellent devitrification resistance, the mass ratio ((Nb ₂ O ₅ + TiO ₂ ) / (SiO ₂ + B ₂ O ₃ ))). The upper limit is preferably 1.800, and more preferably 1.750, 1.700, 1.650, 1.600, 1.550, 1.500, and 1.480 in that order.

When the mass ratio of the content of B ₂ O ₃ to the content of SiO ₂ (B ₂ O ₃ / SiO ₂ ) becomes 1 or more, the chemical durability is lowered, so that the mass ratio (B ₂ O ₃ / SiO ₂ ) ) Is less than 1.
The preferable upper limit of the mass ratio (B ₂ O ₃ / SiO ₂ ) is 0.90, and more preferably 0.70, 0.50, 0.40, 0.30, 0.25 in that order. The preferable lower limit of the mass ratio (B ₂ O ₃ / SiO ₂ ) is 0.00, and further, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0. The order of 07, 0.08, 0.09, 0.10 is more preferable.

In order to maintain the thermal stability and chemical durability of the glass and to achieve the desired optical properties, the SiO ₂ and B ₂ O ₃ with respect to the total content of the SiO ₂ , B ₂ O ₃ and P ₂ O ₅ The mass ratio of the total content (SiO ₂ + B ₂ O ₃ ) / (SiO ₂ + B ₂ O ₃ + P ₂ O ₅ ) is 0.90 or more. The preferable lower limit of the mass ratio (SiO ₂ + B ₂ O ₃ ) / (SiO ₂ + B ₂ O ₃ + P ₂ O ₅ ) is 0.93, and further, in the order of 0.95, 0.97, 0.99. preferable. The mass ratio (SiO ₂ + B ₂ O ₃ ) / (SiO ₂ + B ₂ O ₃ + P ₂ O ₅ ) may be 1.

BaO is an optional component that acts similar to that of CaO. However, when the mass ratio (BaO / CaO) of the BaO content to the CaO content is 1 or more, the specific gravity of the glass increases. Therefore, the mass ratio (BaO / CaO) is less than 1. The preferable upper limit of the mass ratio (BaO / CaO) is 0.98, and more preferably 0.96, 0.94, 0.92 in that order. The preferable lower limit of the mass ratio (BaO / CaO) is 0.00, and further, 0.01, 0.03, 0.05, 0.07, 0.09, 0.10, 0.11, 0.11, 0. It is more preferable in the order of 12, 0.13 and 0.14.

MgO and SrO are components having the same function as CaO and BaO, but the mass ratio of the content of TiO ₂ to the total content of MgO, CaO, SrO and BaO (TiO ₂ / (MgO + CaO + SrO + BaO)) is 0. If it is less than 220, it becomes difficult to obtain the desired high refractive index and high dispersibility while maintaining a low specific gravity. Therefore, the mass ratio (TiO ₂ / (MgO + CaO + SrO + BaO)) is 0.220 or more. The preferable lower limit of the mass ratio (TiO ₂ / (MgO + CaO + SrO + BaO)) is 0.230, and further, 0.240, 0.250, 0.260, 0.270, 0.280, 0.290, 0.295. Is more preferable in the order of.

When the mass ratio (TiO ₂ / (MgO ₊ CaO + SrO + BaO)) becomes too large, the Abbe number νd decreases and the partial dispersion ratio tends to increase. (MgO + CaO + SrO + BaO)) is preferably 1.400, and further, 1.350, 1.300, 1.250, 1.200, 1.150, 1.100, 1.050, 1.000, 0. It is more preferable in the order of .950, 0.900, 0.850, 0.800, 0.750, 0.700.

Ta ₂ O ₅ is a component that increases the refractive index but increases the specific gravity of the glass, and its content is 2% or less, preferably 0 to 1%, and more preferably 0 to 0.1. It is%, and may be 0%.

GeO ₂ has a function of increasing the refractive index, but it is a very expensive component, and its content is 2% or less, preferably 0 to 1%, more preferably 0 to 1% in order to suppress the manufacturing cost of glass. It is 0 to 0.1%, and may be 0%.

In order to obtain a glass having a desired refractive index and Abbe number, the preferable lower limit of the total content of Nb ₂ O ₅ and TiO ₂ is 15%, and further, 17%, 19%, 21% and 23%. More preferred are 25%, 27%, 29% and 31%. The preferred upper limit of the total content of Nb ₂ O ₅ and TiO ₂ is 50%, more preferably 48%, 46%, 44%, 42%, 40% and 38%.

When the glass raw material is melted and melted to form a glass melt and vitrified, or when the glass is heated, softened and remolded after vitrification, crystals _are less likely to precipitate. The content is preferably 10% or more, and more preferably 12% or more, 14% or more, 16% or more, 18% or more, 19% or more, and 20% or more in that order.

If the content of SiO ₂ is too large, the glass raw material tends to remain unmelted or the refractive index tends to decrease. Therefore, it is preferable that the content of SiO ₂ is 40% or less, and further, in the order of 38% or less, 36% or less, 34% or less, 32% or less, 30% or less, 29% or less, and 28% or less. preferable.

The content of B ₂ O ₃ is preferably determined so that the mass ratio (B ₂ O ₃ / SiO ₂ ) is within the above range.

The alkali metal oxide is an optional component that improves the meltability of the glass and, by introducing a small amount, improves the thermal stability of the glass and lowers the liquidus temperature. Therefore, the total content of the alkali metal oxide is preferably more than 0%, more preferably 0.1% or more, and further 0.15% or more, 0.20% or more, 0.25. % Or more, 0.30% or more, 0.35% or more, and 0.40% or more are more preferable.

However, if the total content of the alkali metal oxide exceeds 20%, the thermal stability of the glass will decrease, and crystals will form when the glass melt is formed or when the glass is heated, softened and reformed. There is a tendency for precipitation to occur easily. Therefore, the total content of the alkali metal oxide is preferably 20% or less, and further, 18% or less, 16% or less, 14% or less, 12% or less, 10% or less, 9% or less, 8% or less. , 7% or less, 6% or less, 5% or less, more preferable.

The alkali metal oxide is preferably one or more of Li ₂ O, Na ₂ O, K ₂ O, and Cs ₂ O.

However, since Cs ₂ O is more expensive than other alkali metal oxides, the content of Cs ₂ O is preferably 0 to 1%, more preferably 0 to 0.1%. , 0%.

Since Li ₂ O is the most difficult component to reduce the refractive index among alkali metal oxides, when the total content of alkali metal oxides exceeds 0%, Li ₂ O, Na ₂ O, K ₂ O and The mass ratio of the Li ₂ O content to the total Cs ₂ O content (Li ₂ O / (Li ₂ O + Na ₂ O + K ₂ O + Cs ₂ O)) is preferably 0.01 or more, and further, 0. 02 or more, 0.03 or more, 0.04 or more, 0.06 or more, 0.08 or more, 0.10 or more, 0.20 or more, 0.30 or more, 0.40 or more, 0.50 or more, 0. It is more preferable in the order of 60 or more, 0.70 or more, 0.80 or more, and 0.90 or more.

The preferred upper limit of the Li ₂ O content is 7.0%, further 6.0%, 5.0%, 4.0%, 3.0%, 2.0%, 1.5%, Is more preferable in the order of. The preferred lower limit of the Li ₂ O content is 0.02%, further 0.04%, 0.06%, 0.08%, 0.10%, 0.12%, 0.14%, It is more preferable in the order of 0.15%.

The preferred range of the Na ₂ O content is 0 to 3%, the more preferable range is 0 to 2.8%, and it may be 0%.

The preferred range of K2O content is ₀ to 5%, the more preferred range is 0 to 4.6%, and may be 0%.

The mass ratio of the content of TIO ₂ to the total content of Nb ₂ O ₅ , TIO ₂ , WO ₃ and Bi ₂ O ₃ (TIO ₂ / (Nb ₂ O ₅ + TIO ₂ + WO ₃ + Bi ₂ O ₃ )) is 0. If it is larger than 460, both the refractive index and the dispersion become too high, and the partial dispersion ratio tends to increase. As an optical glass for correcting high-order chromatic aberration, it is not preferable to increase the partial dispersion ratio. In order to suppress the increase in the partial dispersion ratio, the mass ratio (TiO ₂ / (Nb ₂ O ₅ + TiO ₂ + WO ₃ + Bi ₂ O ₃ )) is preferably 0.460 or less, more preferably 0.457 or less. 0.455 or less, 0.453 or less, 0.450 or less, 0.448 or less, 0.446 or less, 0.444 or less, 0.442 or less, 0.440 or less, 0.438 or less, 0.437 or less, It is more preferable in the order of 0.436 or less and 0.435 or less.

On the other hand, compared with TiO ₂ , Nb ₂ O ₅ , WO ₃ , and Bi ₂ O ₃ have a large function of increasing the specific gravity of glass. In addition, Nb ₂ O ₅ , WO ₃ , and Bi ₂ O ₃ tend to deteriorate the transmittance. The mass ratio (TiO ₂ / (Nb ₂ O ₅ + TiO ₂ + WO ₃ + Bi ₂ O ₃ )) is preferably 0.001 or more in order to suppress an increase in the specific gravity and deterioration of the permeability. 0.005 or more, 0.010 or more, 0.030 or more, 0.050 or more, 0.070 or more, 0.090 or more, 0.110 or more, 0.130 or more, 0.150 or more, 0.170 or more, The order of 0.175 or more, 0.180 or more, 0.185 or more, 0.190 or more, and 0.195 or more is more preferable.

Among Nb ₂ O ₅ , TIO ₂ , WO ₃ , and Bi ₂ O ₃ , which are components having a high refractive index and high dispersion, WO ₃ and Bi ₂ O ₃ have a large function of increasing the specific gravity of glass. The mass ratio ((WO ₃ + Bi ₂ O ₃ ) / (Nb ₂ O ₅ + TIO ₂ + WO ₃ + Bi ₂ O ₃ )) is preferably 0.3 or less, preferably 0.1 or less, in order to suppress an increase in specific gravity. It is more preferably 0.05 or less, further preferably 0.020 or less, and particularly preferably 0.010 or less. The mass ratio ((WO ₃ + Bi ₂ O ₃ ) / (Nb ₂ O ₅ + TIO ₂ + WO ₃ + Bi ₂ O ₃ )) may be 0.

When the mass ratio of the ZnO content to the TiO ₂ content (ZnO / TiO ₂ ) is larger than 0.220, the refractive index decreases and the Abbe number increases. From the viewpoint of obtaining desired optical characteristics, the mass ratio (ZnO / TiO ₂ ) is preferably 0.220 or less, more preferably 0.219 or less, 0.218 or less, 0.217 or less, 0.216 or less. , 0.215 or less, 0.214 or less, 0.213 or less, 0.212 or less, 0.211 or less, 0.210 or less, in that order. The mass ratio (ZnO / TiO ₂ ) may be 0.

In order to realize desired optical characteristics and suppress an increase in specific gravity, the preferable range of the Nb ₂ O ₅ content is 8 to 35%, the more preferable range is 10 to 32%, and the TiO ₂ content is preferable. The range is 4 to 22%, and the more preferable range is 6 to 20%.

Further, from the viewpoint of suppressing an increase in the specific gravity of the glass, the lower limit of the mass ratio of the content of TiO ₂ to the content of Nb ₂ O ₅ (TiO ₂ / Nb ₂ O ₅ ) is preferably 0.28. Further, the order of 0.29 and 0.30 is more preferable.

When the amount of the alkaline earth metal oxide component is small, the meltability of the glass is lowered, the unmelted residue of the glass raw material is generated, and the thermal stability of the glass is tended to be lowered. In addition, the refractive index of the glass tends to increase and the Abbe number tends to decrease.

The total content of MgO, CaO, SrO and BaO is preferably 3% or more, more preferably 5 in order to maintain the meltability and thermal stability of the glass and facilitate the realization of desired optical properties. % Or more, 7% or more, 9% or more, 10% or more, 12% or more, 14% or more, 16% or more, 17% or more, 18% or more, and 19% or more are more preferable.

On the other hand, even if the alkaline earth metal oxide component becomes excessive, the meltability and thermal stability of the glass tend to decrease. Excessive introduction of alkaline earth metal oxide components is not preferable from the viewpoint of achieving desired optical properties.

The total content of MgO, CaO, SrO and BaO is preferably 50% or less, more preferably 47, in order to maintain the meltability and thermal stability of the glass and facilitate the realization of desired optical properties. % Or less, 45% or less, 43% or less, 41% or less, 39% or less, 38% or less, 37% or less, 36% or less, 35% or less, 34% or less, in that order.

The preferred range of MgO content is 0 to 10%, more preferably 0 to 9%, 0 to 8%, and 0 to 7%. The content of MgO may be 0%.

Both SrO and BaO have a function of improving the thermal stability of the glass by introducing them into the glass together with CaO. However, when the content of both SrO and BaO becomes excessive, the specific gravity tends to increase.

Therefore, the preferred upper limit of the SrO content is 35%, further 33%, 31%, 29%, 27%, 25%, 23%, 22%, 21%, 17%, 16%, 14%. , 12.2%, 6.2%, more preferred. The content of SrO may be 0%.

With the mass ratio (BaO / CaO) in the above range, the preferable upper limit of the BaO content is 17%, and further, 15%, 13%, and 12% from the viewpoint of further suppressing the increase in the glass specific gravity. , 9%, 8%, 7%, 6%, 5%, 4%, in that order. The BaO content may be 0%.

Further, the preferable upper limit of the total content of SrO and BaO (SrO + BaO) is 27.0%, and further, 26.0%, 25.0%, 24.0%, 23.5%, 23.0%. Is more preferable in the order of. By setting the total content (SrO + BaO) in the above range, an increase in the specific gravity of the glass can be suppressed.

Further, the preferable upper limit of the mass ratio of the CaO content (CaO / (SrO + BaO)) to the total content of SrO and BaO is 27.0, and further, in the order of 21.0, 15.0, 10.0. More preferred. The preferable lower limit of the mass ratio (CaO / (SrO + BaO)) is 0.1, and more preferably 0.3, 0.7, 1.3, and 1.5 in that order. By setting the mass ratio (CaO / (SrO + BaO)) to the above range, an increase in the specific gravity of the glass can be suppressed.

ZnO is a component that works to improve the meltability of glass and adjust the optical properties. It is preferable to determine the content so that the mass ratio (ZnO / TiO ₂ ) is within the above range. The ZnO content may be 0%.

ZrO ₂ is a component that increases the refractive index and decreases the Abbe number. When the content of ZrO ₂ becomes excessive, the meltability of the glass tends to decrease and the thermal stability tends to decrease. From the viewpoint of obtaining the effect of introducing ZrO ₂ , the preferable lower limit of the content of ZrO ₂ is 0.0%, and further, 0.5%, 1.0%, 2.0%, 3.0%, 4 It is more preferable in the order of 0.0%. On the other hand, from the viewpoint of maintaining the meltability and thermal stability of the glass, the preferable upper limit of the ZrO ₂ content is 16.0%, and further, 15.0%, 14.0% and 13.0%. The order of 12.0% and 11.5% is more preferable.

La ₂ O ₃ is a component that increases the refractive index and increases the Abbe number as compared with ZrO _2, Nb ₂ O ₅ , and TiO ₂ . From the viewpoint of obtaining desired optical characteristics, the preferable lower limit of the content of La ₂ O ₃ is 0.5%, and further, 1.0%, 1.5%, 1.7%, 2.0%, and the like. It is more preferable in the order of 2.2%, 2.4% and 2.6%. When the content of La ₂ O ₃ becomes excessive, the meltability and thermal stability of the glass tend to decrease. It also shows a tendency for the specific density to increase. Therefore, the preferred upper limit of the La ₂ O ₃ content is 24%, and more preferably 22%, 20%, 18%, 16%, 14%, 13%, 12%, and 11%.

Further, from the viewpoint of suppressing an increase in the specific gravity of the glass, the upper limit of the mass ratio of the content of La ₂ O ₃ (La ₂ O ₃ / (CaO + BaO)) to the total content of CaO and BaO is preferably 0.670. Further, it is more preferable in the order of 0.665, 0.660, 0.655.

Gd ₂ O ₃ , Y ₂ O ₃ , Yb ₂ O ₃ , and Lu ₂ O ₃ can all be introduced in a small amount, but by introducing these components, the specific gravity of the glass is increased and the meltability is lowered. The content of each of the above components is preferably 0 to 5%, more preferably 0 to 2%, further preferably 0 to 1%, and 0 to 0 to 1, respectively. It is more preferably 0.1%. The content of each component of Gd ₂ O ₃ , Y ₂ O ₃ , Yb ₂ O ₃ , and Lu ₂ O ₃ may be 0%, respectively.

(Other ingredients)
In addition to the above components, the above optical glass may also contain a small amount of Sb ₂ O ₃ , CeO ₂ , etc. as a clarifying agent. The total amount of the clarifying agent (the amount of external split added) is preferably 0% or more and less than 1%, and more preferably 0% or more and 0.5% or less.

The external split addition amount is the amount of the clarifying agent added when the total content of all glass components excluding the clarifying agent is 100%, expressed as a percentage by weight.

Pb, Cd, As, Th and the like are components that are concerned about environmental load. Therefore, the contents of PbO, CdO, and ThO ₂ , respectively, are preferably 0 to 0.1%, more preferably 0 to 0.05%, and 0 to 0.01%, respectively. Is more preferable, and it is particularly preferable that PbO, CdO, and ThO ₂ are not substantially contained.

The content of As ₂ O ₃ is preferably 0 to 0.1%, more preferably 0 to 0.05%, further preferably 0 to 0.01%, and As ₂ O. It is particularly preferable that ₃ is not substantially contained.

Further, the optical glass can obtain high transmittance over a wide range of the visible region. In order to take advantage of these features, it is preferable that they do not contain coloring elements. Examples of the coloring element include Cu, Co, Ni, Fe, Cr, Eu, Nd, Er, and V. Each element is preferably less than 100 mass ppm, more preferably 0 to 80 mass ppm, further preferably 0 to 50 mass ppm or less, and particularly preferably not substantially contained. ..

Further, Hf, Ga, Te, Tb and the like are components that do not need to be introduced and are also expensive components. Therefore, the range of the contents of HfO ₂ , Ga ₂ O ₃ , TeO ₂ , and TbO ₂ in terms of mass% is preferably 0 to 0.1%, and is preferably 0 to 0.05%, respectively. More preferably, it is further preferably 0 to 0.01%, further preferably 0 to 0.005%, further preferably 0 to 0.001%, and substantially contained. Not particularly preferred.

[Abbe number νd, refractive index nd]
The optical glass preferably has an Abbe number νd in the range of 27 or more, more preferably 28 or more, in order to correct chromatic aberration in combination with a lens made of glass having other optical characteristics. It is more preferably in the range of more than 29. The preferred upper limit of the Abbe number νd is 33, the more preferred upper limit is 32, the more preferred upper limit is 31.5, the more preferred upper limit is 30.6, the even more preferred upper limit is 30.5, and the further preferred upper limit is 30.4. ..

An optical glass having a high refractive index nd is desired because the absolute value of the curvature of the optical functional surface of the lens can be reduced (the curve of the optical functional surface of the lens is loosened) while having the same light-collecting power. In the preferred embodiment of the optical glass, the preferred lower limit of the refractive index nd is 1.80, and the more preferable lower limit is 1.81.

On the other hand, if the refractive index is excessively high, the relative ratio of the high refractive index components becomes high, and the specific gravity of the glass increases. In the preferred embodiment of the optical glass, the preferred upper limit of the refractive index nd is 1.87, and the more preferable upper limit is 1.86 from the viewpoint of suppressing the increase in the specific gravity.
In order to obtain an optical glass having the above characteristics and the following characteristics, it is preferable that the refractive index nd and the Abbe number νd satisfy the following equations.
nd≤4.30-0.08 × νd

[Partial dispersion ratio Pg, F]
Using the refractive indexes ng, nF, and nC of the g-line, F-line, and c-line, the partial dispersion ratios Pg and F are expressed as follows.
Pg, F = (ng-nF) / (nF-nC)
The normal line is expressed by the following equation in a plane having the Abbe number νd on the horizontal axis and the partial dispersion ratios Pg and F on the vertical axis.
Pg, F (0) = 0.6483- (0.0018 × νd)
Further, the deviations ΔPg and F of the partial dispersion ratios Pg and F from the normal line are expressed as follows.
ΔPg, F = Pg, F-Pg, F (0)

In order to provide optical glass suitable for high-order chromatic aberration correction, the preferable upper limit of the partial dispersion ratios Pg and F is 0.64, and further, 0.63, 0.62, 0.61 and 0.60. Is more preferable in the order of. The preferred lower limit of the partial dispersion ratios Pg and F is 0.54, and more preferably 0.55, 0.56, 0.57 and 0.58 in that order.

The preferred upper limit of ΔPg and F is 0.0090, and more preferably 0.0080, 0.0070, 0.0060, and 0.0050. The preferable lower limit of ΔPg and F is 0.0000, and more preferably 0.0003, 0.0005, 0.0007, and 0.0010.

[Transmittance]
The optical glass is an optical glass with very little coloring. Such optical glass is suitable as a material for an optical element for imaging such as a camera lens and an optical element for projection such as a projector.

Generally, the degree of coloring of optical glass is represented by λ70, λ5, or the like. The spectral transmittance of a glass sample with a thickness of 10.0 mm ± 0.1 mm is measured in the wavelength range of 200 to 700 nm. The wavelength at which the external transmittance is 70% is λ70, and the wavelength at which the external transmittance is 5% is λ5. And.
The preferable range of λ70 of the optical glass is 650 nm or less, and the preferable range of λ5 is 400 nm or less.

[Glass transition temperature Tg]
A preferred embodiment of the optical glass is an optical glass having a glass transition temperature Tg of 750 ° C. or lower. When the glass transition temperature is low, the heating temperature at the time of reheating and softening the glass and press-molding can be lowered. As a result, it becomes easy to suppress the fusion between the glass and the press molding die. Further, since the heating temperature can be lowered, it is possible to reduce the thermal consumption of the glass heating device, the press molding die, and the like. Further, since the annealing temperature of the glass can be lowered, the life of the annealing furnace can be extended. A more preferable range of the glass transition temperature is 740 ° C. or lower.

[Liquid phase temperature]
A preferred embodiment of the optical glass is an optical glass having excellent thermal stability and a liquid phase temperature of 1400 ° C. or lower. When the liquidus temperature is low, the melting and molding temperature of the glass can be lowered. Along with this, it becomes possible to reduce the erosion of bricks, crucibles such as platinum, and glass melting equipment in the melting process. As a result, it is possible to suppress the mixing of foreign substances (for example, refractories constituting bricks, platinum foreign substances, platinum ions) into the glass.

A more preferable range of the liquid phase temperature is 1350 ° C. or lower, and more preferably 1300 ° C. or lower, 1250 ° C. or lower, and 1200 ° C. or lower.

[specific gravity]
A preferred embodiment of the optical glass is an optical glass having a specific gravity of 4.40 or less. A more preferable range of the specific density is 4.30 or less, and further, 4.20 or less, 4.15 or less, 4.10 or less, 4.05 or less, 4.00 or less, 3.95 or less, 3.90 or less. It is more preferably 3.85 or less, 3.81 or less, 3.80 or less, and 3.75 or less.

[Use]
A preferred embodiment of the optical glass is an optical glass for an optical lens or an optical glass for a prism.

[Production method]
The optical glass can be obtained, for example, by blending, melting, and molding a glass raw material so as to obtain required characteristics. As the glass raw material, for example, oxides, carbonates, nitrates, sulfates and the like can be used. As a glass melting method and a molding method, known methods can be used.

[Glass material for press molding and its manufacturing method, and manufacturing method of glass molded body]
According to one aspect of the present invention, it is possible to provide a glass material for press molding made of the optical glass, a glass molded body made of the optical glass, and a method for producing the same.

The press forming of the glass material for press forming can be performed by pressing the glass material for press forming, which is in a softened state by heating, with a press forming die. Both heating and press molding can be performed in the atmosphere. By uniformly applying a powder release agent such as boron nitride to the surface of the glass material for press molding, heating and press molding, fusion of the glass and the molding mold can be reliably prevented, and the molding surface of the press molding mold can be prevented. The glass can be stretched smoothly along the line. By annealing after press molding to reduce the strain inside the glass, a homogeneous optical element blank can be obtained.

Examples of the glass material for press forming include a preform for precision press forming, a glass material for press forming an optical element blank (glass gob for press forming), and the like, and the mass corresponding to the mass of the target press-molded product. A glass block having a.

In addition, glass materials for press molding are also called preforms, and in addition to those that are subjected to press molding as they are, those that are subjected to press molding by machining such as cutting, grinding, and polishing are also available. include. As a cutting method, a groove is formed on the surface of the glass plate to be cut by a method called scribing, and a local pressure is applied from the back surface of the surface on which the groove is formed to the groove portion to apply a local pressure to the groove portion to make glass. There are methods such as breaking the plate and cutting the glass plate with a cutting blade. Further, examples of the grinding method include spherical surface processing and smoothing processing using a curve generator. Examples of the polishing method include polishing using abrasive grains such as cerium oxide and zirconium oxide.

[Optical element blank and its manufacturing method]
According to one aspect of the present invention, it is possible to provide an optical element blank made of the above optical glass. The optical element blank is a glass molded body having a shape similar to the shape of the optical element to be manufactured. The optical element blank can be produced by a method of forming glass into a shape to which a processing allowance to be removed when processing the shape of the optical element to be manufactured is added. For example, an optical element by a method of heating and softening a glass material for press molding and press forming (reheat pressing method), a method of supplying a molten glass block to a press forming die by a known method (direct pressing method), and the like. Blanks can be made.

[Optical element and its manufacturing method]
According to one aspect of the present invention, it is possible to provide an optical element made of the above optical glass. Examples of the type of optical element include a spherical lens, a lens such as an aspherical lens, a prism, a diffraction grating, and the like. As the shape of the lens, various shapes such as a biconvex lens, a plano-convex lens, a biconcave lens, a plano-concave lens, a convex meniscus lens, and a concave meniscus lens can be exemplified. The optical element can be manufactured by a method including a step of processing a glass molded body made of the above optical glass. Examples of processing include cutting, cutting, rough grinding, fine grinding, and polishing. By using the above-mentioned glass during such processing, damage can be reduced and high-quality optical elements can be stably supplied.

Hereinafter, the present invention will be described in more detail by way of examples. However, the present invention is not limited to the embodiments shown in the examples.

(Example 1)
As the raw materials for introducing each component, the corresponding oxides and the like were used so as to have the glass composition shown in Table 1, the raw materials were weighed, and the raw materials were sufficiently mixed to prepare a compounding raw material.

This compounding material was placed in a platinum crucible, heated and melted. After melting, the molten glass is poured into a mold, allowed to cool to near the glass transition temperature, and then immediately placed in an annealing furnace. After annealing around the glass transition temperature for about 30 minutes to about 2 hours, the glass is allowed to cool to room temperature in the furnace. By doing so, each optical glass of sample numbers 1 to 108 shown in Tables 1-1, 1-2, and 1-3 was obtained.

When the obtained optical glass was magnified and observed with an optical microscope, no crystal precipitation, foreign substances such as platinum particles derived from the platinum crucible, and bubbles were observed, and no pulse was observed.
The characteristics of the optical glass thus obtained are shown in Table 2-1-1, 2-1-2, 2-2-1, 2--2-2, 2-3-1, 2-3-2. show.

Various characteristics of the optical glass were measured by the methods shown below.
(I) Refractive index nd, ng, nF, nC and Abbe number νd
Refractive indexes nd, ng, nF, and nC were measured for the glass obtained by lowering the temperature at a temperature lowering rate of -30 ° C / hour by the refractive index measurement method of JIS standard JIS B 7071-1, and based on the formula (1). The Abbe number νd was calculated.
νd = (nd-1) / (nF-nC) ... (1)

(Ii) Partial dispersion ratio Pg, F
The partial dispersion ratios Pg and F were calculated based on the equation (2) using the refractive indexes ng, nF and nC of the g-line, the F-line and the c-line.
Pg, F = (ng-nF) / (nF-nC) ... (2)
It was confirmed that the partial dispersion ratios Pg and F were in the range of 0.5935 to 0.6010 in all the samples.

(Iii) Deviation ΔPg, F of partial dispersion ratio Pg, F
It was calculated based on the equation (3) using the partial dispersion ratios Pg, F and the Abbe number νd.
ΔPg, F = Pg, F + (0.0018 × νd) −0.6483 ・ ・ ・ (3)
It was confirmed that ΔPg and F were in the range of 0.0007 to 0.0065 in all the samples.

(Iv) Glass transition temperature Tg
Measurement was performed at a heating rate of 10 ° C./min using a differential scanning calorimetry device (DSC8270) manufactured by Rigaku.

(V) λ70, λ5
The obtained optical glass was processed to have a thickness of 10 mm and having planes parallel to each other and optically polished, and the spectral transmittance in the wavelength range from 280 nm to 700 nm was measured. The spectral transmittance B / A was calculated with the intensity A of the light beam perpendicularly incident on one of the optically polished planes as the intensity A and the intensity of the light rays emitted from the other plane as the intensity B. The wavelength at which the spectral transmittance is 70% is λ70, and the wavelength at which the spectral transmittance is 5% is λ5. The spectral transmittance also includes the reflection loss of light rays on the sample surface.

(Vi) Relative density Measured by Archimedes method.

(Example 2)
Using a glass melting furnace equipped with a refractory melting tank, a platinum alloy clarification tank, and a working tank (stirring tank), the batch raw materials prepared so that each optical glass produced in Example 1 can be obtained are used in the melting tank. It was thrown in to melt the glass.

The batch raw material is melted in the melting tank to become molten glass, and in the process of flowing from the melting tank to the clearing tank and from the clearing tank to the working tank through the pipe connecting the melting tank and the clearing tank, and the clearing tank and the working tank. It was clarified, homogenized, and poured into a molding mold through an outflow pipe attached to the bottom of the working tank.

Glass was molded with a mold, and the molded glass was annealed to obtain optical glass. When the obtained optical glass was observed, no unmelted raw material, no refractory mixture, and no crystal precipitation was observed.

In this way, each optical glass obtained in Example 1 was produced using a continuous glass melting furnace. The glass melting furnace has a known structure.

(Example 3)
Using each optical glass produced in Example 2, a lens blank was produced by a known method, and the lens blank was processed by a known method such as polishing to produce various lenses.
The manufactured optical lenses are various lenses such as a biconvex lens, a biconcave lens, a plano-convex lens, a plano-concave lens, a concave meniscus lens, and a convex meniscus lens.
By combining various lenses with lenses made of other types of optical glass, high-order chromatic aberration could be satisfactorily corrected.

In addition, since glass has a low specific density, each lens is lighter in weight than a lens having the same optical characteristics and size, and is suitable for various imaging devices, especially for autofocus type imaging devices because it can save energy. be. Similarly, a prism was produced using various optical glasses produced in Example 2.

It should be considered that the embodiments disclosed this time are exemplary in all respects and not restrictive. The scope of the present invention is shown by the scope of claims rather than the above description, and is intended to include all modifications within the meaning and scope equivalent to the scope of claims.

For example, the optical glass according to one aspect of the present invention can be produced by adjusting the composition described in the specification with respect to the glass composition exemplified above.
In addition, it is of course possible to arbitrarily combine two or more of the items described in the specification as an example or a preferable range.

Claims (6)

It contains SiO ₂ , Nb ₂ O ₅ , TiO ₂ , and CaO as essential components.
The total content of Nb ₂ O ₅ and TIO ₂ is 31.000% by mass or more, 38.000% by mass or less,
The mass ratio of the total content of Nb ₂ O ₅ and TIO ₂ to the total content of SiO ₂ and B ₂ O ₃ ((Nb ₂ O ₅ + TiO ₂ ) / (SiO ₂ + B ₂ O ₃ )) is 1.120 or more. , 1.500 or less,
The mass ratio of the content of B ₂ O ₃ to the content of SiO ₂ (B ₂ O ₃ / SiO ₂ ) is less than 1,
Mass ratio of total content of SiO ₂ and B ₂ O ₃ to total content of SiO ₂ , B ₂ O ₃ and P ₂ O ₃ (SiO ₂ + B ₂ O ₃ ) / (SiO ₂ + B ₂ O ₃ + P ₂ O) ₅ ) is 0.9 or more,
The mass ratio of BaO content to CaO content (BaO / CaO) is less than 1,
The mass ratio of the content of TiO ₂ to the total content of MgO, CaO, SrO and BaO (TiO ₂ / (MgO + CaO + SrO + BaO)) is 0.220 or more, 0.66 or less,
The mass ratio of the content of La 2 O 3 (La ₂ O _{3 /} ( _CaO + BaO)) to the total content of CaO and BaO is 0.716 or less,
Li ₂ O content is 6.0% by mass or less,
CaO content is 15.5% by mass or more,
BaO content is 11.924% by mass or less,
Ta ₂ O ₅ content is 2% by mass or less,
An optical glass having a GeO ₂ content of 2% by mass or less. The mass ratio of the content of TIO ₂ to the total content of Nb ₂ O ₅ , TiO ₂ , WO ₃ and Bi ₂ O ₃ (TiO ₂ / (Nb ₂ O ₅ + TiO ₂ + WO ₃ + Bi ₂ O ₃ )) is 0. The optical glass according to claim 1, which is 460 or less . The optical glass according to claim 1 or 2, wherein the content of SiO ₂ is 10 to 40% by mass. The optical glass according to any one of claims 1 to 3, wherein the total content of the alkali metal oxide exceeds 0% by mass. La ₂ O ₃ The optical glass according to any one of claims 1 to 4, wherein the content of the glass is 2.779% by mass or more. The optical element made of the optical glass according to any one of claims 1 to 5 .