JP2020029378A - Optical glass - Google Patents

Abstract

To provide an optical glass having desired optical property and good in transmittance.SOLUTION: There is provided an optical glass containing, by mol%, SiOof 1.5 to 60%, BOof 1 to 30%, TaOof 0 to 15%, NbOof 12 to 35%, TiOof 0 to 15%, and NaO+KO+LiO of 0.1 to 40%, and practically no lead component, arsenic component, nor fluorine component.SELECTED DRAWING: None

Description

  The present invention relates to an optical glass suitable as an optical lens of a digital camera or a video camera, a lens for optical communication, and the like.

  In recent years, digital cameras and video cameras have been increasingly improved in performance, specifically, downsizing, higher magnification, higher definition, and the like. In order to achieve such high performance, glass for optical lenses used in digital cameras and video cameras is often required to have characteristics such as high refractive index, high dispersion, and extraordinary dispersion. .

As a glass satisfying the above characteristics, for example, a SiO ₂ —TiO ₂ —Nb ₂ O ₅ system glass having a refractive index (nd) of 1.75 or more and an Abbe number (νd) of 35 or less has been proposed (for example, Patents). Reference 1).

JP 2009-203134 A

The conventional SiO ₂ —TiO ₂ —Nb ₂ O ₅ -based glass has desired optical properties, but has a problem that it has low transmittance and hinders use as an optical lens.

  In view of the above problems, an object of the present invention is to provide an optical glass having desired optical characteristics and having good transmittance.

The optical glass of the present invention, in _{mol%, SiO 2 1.5~60%, B} 2 O 3 1~30%, Ta 2 O 5 0~15%, Nb 2 O 5 12~35%, TiO 2 0 15%, and _{Li 2 O + Na 2 O +} K 2 contain O 0.1 to 40%, and wherein lead component, arsenic component, that is substantially free of fluorine component.

As a result of the investigations by the present inventors, the main cause of the decrease in transmittance in the SiO ₂ —TiO ₂ —Nb ₂ O ₅ -based glass is that a large amount of TiO _2, which is a component for increasing the refractive index and dispersion, is contained. I found out what was being done. Therefore, while reducing the content of TiO ₂ as much as possible, and containing a large amount of Nb ₂ O ₅ , which is also a component that also enhances the refractive index and dispersion, SiO ₂ —Nb ₂ O ₅ —R ₂ O (R is Li, Na Or, it has been found that a K) -based glass can achieve high transmittance while achieving high refractive index and high dispersion optical characteristics. In addition, the weather resistance is improved, and the physical properties are not easily deteriorated and the surface is not easily deteriorated during the manufacturing process or during use of the product. Further, by containing Nb ₂ O ₅ as an essential component, it becomes possible to obtain a glass having excellent anomalous dispersibility (ie, having a low partial dispersion ratio).

  The optical glass of the present invention preferably further contains 0 to 10% of MgO + CaO + SrO + BaO + ZnO in mol%.

It is preferable that the optical glass of the present invention further contains 0 to 15% of ZrO _{2 and} 0 to 10% of Al ₂ O ₃ in mol%.

The optical glass of the present invention may further contain, as a glass composition, 0 to 10% by mass% of La ₂ O ₃ + Gd ₂ O ₃ + Bi ₂ O ₃ + Y ₂ O ₃ + Yb ₂ O ₃ + TeO ₂ + GeO _2. preferable.

The optical glass of the present invention preferably has a molar ratio of Nb ₂ O ₅ / Ta ₂ O ₅ of 350 or less.

The optical glass of the present invention preferably has a molar ratio of TiO ₂ / Nb ₂ O ₅ of 1.2 or less.

  The optical glass of the present invention preferably has a refractive index of 1.75 to 1.95 and an Abbe number of 15 to 35.

  The optical glass of the present invention preferably has a partial dispersion ratio of 0.645 or less.

  In the optical glass of the present invention, it is preferable that the partial dispersion ratio (θg, F) and the Abbe number (νd) satisfy the relational expression of (θg, F) <− 0.0041 × (νd) +0.7190.

The optical glass of the present invention, it is preferable degree of coloration lambda ₇₀ is less than 480 nm.

  According to the present invention, it is possible to provide an optical glass having desired optical characteristics and good transmittance.

  Hereinafter, the reason for limiting the content of each component in the optical glass of the present invention as described above will be described. Unless otherwise specified, “%” in the following description means “mol%”.

SiO ₂ is a component that forms a glass skeleton. Further, it has an effect of improving weather resistance, and particularly has a high effect of suppressing a component such as an alkali metal oxide in glass from being selectively eluted into water. Further, it has the effect of lowering the liquidus temperature and suppressing devitrification. The content of SiO ₂ is 1.5 to 60%, preferably 2.5 to 57.5%, 5 to 55%, 7.5 to 30%, and particularly preferably 10 to 27.5%. If the content of SiO ₂ is too small, it is difficult to obtain the above effects. On the other hand, if the content of SiO ₂ is too large, the meltability is reduced, and striae and bubbles due to undissolution are likely to remain in the glass, which may not satisfy the required quality as glass for lenses. Further, the partial dispersion ratio tends to increase.

B ₂ O ₃ is a component that forms a glass skeleton similarly to SiO ₂ . Further, compared to SiO ₂ , it is difficult to increase the partial dispersion ratio. The content of B ₂ O ₃ is 1 to 30%, preferably 1.5 to 25%, 2.5 to 20%, particularly preferably 5 to 17.5%. If the content of B ₂ O ₃ is too small, vitrification tends to be difficult. On the other hand, if the content of B ₂ O ₃ is too large, it tends to evaporate during melting, making it difficult to obtain a homogeneous glass.

Ta ₂ O ₅ is a component for achieving high refractive index and high dispersion, and is a component having a high effect of lowering the partial dispersion ratio. Further, among the components that can achieve a high refractive index, they are components that are relatively hard to raise the liquidus temperature (hardly cause devitrification). The content of Ta ₂ O ₅ is 0 to 15%, preferably 0.5 to 13%, 1 to 11%, and particularly preferably 1.5 to 9%. If the content of Ta ₂ O ₅ is too large, the liquidus temperature rises, and crystals containing Ta ₂ O ₅ as a main component tend to precipitate, and vitrification tends to be difficult.

Nb ₂ O ₅ is a component for achieving a high refractive index and a high dispersion, and is a component having a high effect of lowering the partial dispersion ratio. The content of Nb ₂ O ₅ is an 12-35%, 13 to 32.5%, 15% to 30%, from 17 to 27.5%, from 19 to 26%, particularly preferably 20-25%. If the content of Nb ₂ O ₅ is too small, it is difficult to obtain the above effects. On the other hand, if the content of Nb ₂ O ₅ is too large, the liquidus temperature rises and crystals containing Nb ₂ O ₅ as a main component tend to be precipitated, and vitrification tends to be difficult.

TiO ₂ is a component for achieving high refractive index and high dispersion, and also has an effect of reducing the partial dispersion ratio. Further, there is an effect of suppressing coloring of the glass due to ultraviolet light. The content of TiO ₂ is 0 to 15% from 0.1 to 12.5%, 0.5% to 10%, particularly preferably from 1 to 8.5%. If the content of TiO ₂ is too large, the devitrification resistance tends to decrease and vitrification tends to be difficult. Further, the visible light transmittance tends to decrease.

Among the Ta ₂ O ₅ , Nb ₂ O ₅ , and TiO ₂ , the component having the greatest effect of lowering the partial dispersion ratio is Ta ₂ O ₅ , Nb ₂ O ₅ , and then TiO ₂ .

In the optical glass of the present invention, it is preferable to appropriately adjust the total amount of Nb ₂ O ₅ and Ta ₂ O ₅ (Nb ₂ O ₅ + Ta ₂ O ₅ ) in order to achieve a low partial dispersion ratio. Specifically, Nb ₂ O ₅ + Ta ₂ O ₅ is preferably at least 12%, at least 14%, at least 16%, particularly preferably at least 18%.

In the optical glass of the present invention, in order to achieve a low partial dispersion ratio, it is preferable to appropriately adjust the ratio between the respective contents of Nb ₂ O ₅ and Ta ₂ O ₅ , and between TiO ₂ and Nb ₂ O ₅ . Specifically, the molar ratio of Nb ₂ O ₅ / Ta ₂ O ₅ is 350 or less, 200 or less, 100 or less, 50 or less, 40 or less, 30 or less, 20 or less, 18 or less, particularly 16 or less. preferable. The molar ratio of TiO ₂ / Nb ₂ O ₅ is preferably 1.2 or less, 1.1 or less, particularly preferably 1 or less. If any one of Nb ₂ O ₅ / Ta ₂ O ₅ and TiO ₂ / Nb ₂ O ₅ is larger than the above range, it becomes difficult to obtain a low partial dispersion ratio. Further, the visible light transmittance tends to decrease.

Li ₂ O, Na ₂ O, and K ₂ O are components that lower the partial dispersion ratio. In addition, there is an effect of lowering the softening point and facilitating vitrification. The total amount of Li ₂ O, Na ₂ O, and K ₂ O (Li ₂ O + Na ₂ O + K ₂ O) is 0.1 to 40%, 0.5 to 37.5%, 1 to 35%, and 1.0. It is preferably from 5 to 32.5%, particularly preferably from 2 to 30%. If the total amount of Li ₂ O, Na ₂ O, and K ₂ O is too small, it is difficult to obtain the above effects. On the other hand, if the total amount of Li ₂ O, Na ₂ O, and K ₂ O is too large, the chemical durability tends to decrease. Further, it becomes difficult to obtain optical characteristics having a high refractive index and a high dispersion.

The contents of Li ₂ O, Na ₂ O, and K ₂ O are 0 to 40%, 0.1 to 37.5%, 0.5 to 35%, and 1 to 32.5%, respectively. And particularly preferably 1.5 to 30%.

  The optical glass of the present invention can contain the following components in addition to the above components.

  Since MgO, CaO, SrO, BaO, and ZnO form a glass skeleton as an intermediate oxide, they have an effect of improving devitrification resistance and improving chemical durability. However, since these components increase the partial dispersion ratio, if the content is too large, it becomes difficult to obtain desired optical characteristics. Therefore, the total amount (MgO + CaO + SrO + BaO + ZnO) of MgO, CaO, SrO, BaO, and ZnO is 0 to 10%, 0 to 8%, 0.1 to 7, 5%, especially 0.5 to 6.5%. Is preferred.

  In addition, the content of each component of MgO, CaO, SrO, BaO, and ZnO is 0 to 10%, 0 to 8%, 0.1 to 7, 5%, and particularly 0.5 to 6.5%. Preferably, there is.

ZrO ₂ is a component that increases the refractive index and also has the effect of lowering the partial dispersion ratio. Further, it has an effect of improving weather resistance, and particularly has a high effect of suppressing a component in glass from being selectively eluted into water. The content of ZrO ₂ 0 to 15% 0.5 to 14%, from 1 to 12.5%, particularly preferably 2-12%. If the content of ZrO ₂ is too large, devitrification tends to occur. Further, the meltability may be reduced, and striae and bubbles may remain in the glass, and may not satisfy the required quality as glass for lenses.

In order to achieve a low partial dispersion ratio, it is preferable to appropriately adjust the ratio between the total amount of Nb ₂ O ₅ and Ta ₂ O ₅ (Nb ₂ O ₅ + Ta ₂ O ₅ ) and the content of ZrO ₂ . Specifically, the molar ratio of (Nb ₂ O ₅ + Ta ₂ O ₅ ) / ZrO ₂ is 1 or more, 1.5 or more, 2 or more, 3 or more, 5 or more, 7.5 or more, particularly 10 or more. Is preferred. When (Nb ₂ O ₅ + Ta ₂ O ₅ ) / ZrO ₂ is smaller than the above range, it becomes difficult to obtain a low partial dispersion ratio. Further, the visible light transmittance tends to decrease.

Al ₂ O ₃ is a component capable of forming a glass skeleton similarly to SiO ₂ . Further, it has an effect of improving weather resistance, and particularly has a high effect of suppressing a component in glass from being selectively eluted into water. In addition, the addition of a small amount has an effect of suppressing devitrification. The content of Al ₂ O ₃ is preferably 0 to 10%, particularly preferably 0.1 to 5%. If the content of Al ₂ O ₃ is too large, devitrification tends to occur. Further, the meltability may be reduced, and striae and bubbles may remain in the glass, and may not satisfy the required quality as glass for lenses.

La ₂ O ₃ , Gd ₂ O ₃ , Bi ₂ O ₃ , Y ₂ O ₃ , Yb ₂ O ₃ , TeO ₂ , and GeO ₂ are components that increase the refractive index. However, since these components increase the partial dispersion ratio, if the content is too large, it becomes difficult to obtain desired optical characteristics. Therefore, the total amount of La ₂ O ₃ , Gd ₂ O ₃ , Bi ₂ O ₃ , Y ₂ O ₃ , Yb ₂ O ₃ , TeO ₂ and GeO ₂ (La ₂ O ₃ + Gd ₂ O ₃ + Bi ₂ O ₃ + Y _{2 O 3 + Yb 2 O 3} + TeO 2 + GeO 2) is 0-10%, 0-9% 0.1 to 8%, particularly preferably 0.5% to 5%.

The contents of La ₂ O ₃ , Gd ₂ O ₃ , Bi ₂ O ₃ , Y ₂ O ₃ , Yb ₂ O ₃ , TeO ₂ , and GeO ₂ are respectively 0 to 10% and 0 to 9%. %, 0.1 to 8%, particularly preferably 0.5 to 5%.

P ₂ O ₅ is a component that forms a glass skeleton, and has an effect of suppressing devitrification and improving weather resistance. It also has the effect of increasing the Abbe number. However, if the content of P ₂ O ₅ is too large, the weather resistance tends to be rather reduced. In addition, the refractive index decreases, and the softening point increases, so that mold press molding at low temperatures tends to be difficult. Furthermore, the partial dispersion ratio tends to increase unduly. Therefore, the content of P ₂ O ₅ is preferably 0 to 10%, particularly preferably 0 to 5%.

WO ₃ is a component for achieving high refractive index and high dispersion, and also has an effect of lowering the partial dispersion ratio. Further, coloring due to ultraviolet light can be suppressed. However, if the content is too large, the devitrification resistance tends to decrease, making vitrification difficult, or the transmittance in the ultraviolet region tends to decrease. Further, the affinity with the press mold is increased, and the glass tends to be easily fused to the mold during mold press molding. Accordingly, the content of WO ₃ 0 to 30% 0.1 to 29%, from 0.5 to 28%, particularly preferably from 1 to 27.5%.

As a fining agent, for example, Sb ₂ O ₃ , SnO ₂ , CeO ₂ , NO ₃ , or SO ₃ can be contained. If the amount of Sb ₂ O ₃ is very small, it also has the effect of improving the transmittance in the visible region. However, if the content of the fining agent is too large, undesired coloring may occur. Therefore, the content of each of these components is preferably 1% or less.

A lead component (for example, PbO), an arsenic component (for example, As ₂ O ₃ ), and a fluorine component (for example, F ₂ ) have a large load on the environment and are substantially not contained because there is a concern that the glass may be colored. (Specifically, each less than 0.1%).

When the optical glass of the present invention is used as a lens, the thickness can be reduced as the refractive index increases, which is advantageous in reducing the size of the optical device. Therefore, the refractive index (nd) of the optical glass of the present invention is preferably 1.75 or more, 1.775 or more, 1.785 or more, and particularly preferably 1.8 or more. On the other hand, in order to improve the refractive index, it is necessary to contain a large amount of components that make the glass unstable, such as Nb ₂ O _5. Therefore, it is necessary to define the upper limit of the refractive index in consideration of the stability of the glass. is there. Specifically, the refractive index of the optical glass of the present invention is preferably 1.95 or less, particularly preferably 1.9 or less.

  The Abbe number of the optical glass of the present invention is preferably 35 or less, 30 or less, 26 or less, and particularly preferably 24 or less. In addition, as the Abbe number is lower, the optical design is advantageous in reducing the chromatic aberration in combination with another lens, but on the other hand, the refractive index tends to decrease and the glass tends to be unstable. Therefore, the Abbe number of the optical glass of the present invention is preferably 15 or more, 18 or more, 20 or more, 21 or more, particularly preferably 22 or more.

  In order to correct chromatic aberration in an optical device, it is common to use a low dispersion glass and a high dispersion glass in combination. Here, it is known that chromatic aberration can be more effectively corrected by using glass having a small partial dispersion ratio as the high dispersion glass. Therefore, the partial dispersion ratio (θg, F) of the optical glass of the present invention is preferably 0.645 or less, 0.63 or less, 0.62 or less, and particularly preferably 0.615 or less.

  It is preferable that the partial dispersion ratio (θg, F) and the Abbe number (νd) satisfy the relational expression of (θg, F) <− 0.0041 × (νd) +0.7190. This makes it possible to more effectively correct the chromatic aberration.

The optical glass of the present invention preferably has a low degree of coloration lambda _70. As a result, the transmittance in the visible region and the near-ultraviolet region increases, and the chromatic aberration decreases, which is suitable for optical elements such as various optical lenses. Specifically, the coloring degree λ ₇₀ of the optical glass of the present invention is preferably less than 480 nm, 470 nm or less, particularly preferably 460 nm or less. In the present invention, the coloring degree λ ₇₀ refers to the shortest wavelength at which the light transmittance becomes 70% in a light transmittance curve measured using a sample having a thickness of 10 mm.

  In addition to the characteristics described above, the optical glass of the present invention preferably has a low glass transition point. Thereby, fusion with a mold at the time of mold press molding can be suppressed, and mass productivity can be improved. Further, as the glass transition point is lower, the glass component is less likely to volatilize during mold press molding, so that problems such as lowering of molding accuracy and deterioration or contamination of the mold are less likely to occur. Specifically, the glass transition point of the optical glass of the present invention is preferably 700 ° C. or lower, particularly preferably 650 ° C. or lower.

  Next, a method for manufacturing an optical lens used for a digital camera, a video camera, or the like using the optical glass of the present invention will be described.

  First, a glass material prepared to have a desired composition is melted. Next, the molten glass is dropped from the tip of the nozzle and formed into a droplet (droplet forming) to obtain a glass material. After the obtained glass material is polished or molded without being polished, an optical lens having a predetermined shape is obtained. Instead of performing droplet forming, a method of forming molten glass into an ingot, polishing a glass material cut out to an appropriate size, and then performing mold press forming may be employed.

  An optical lens made from the optical glass of the present invention can be assembled to a metal part and used as a lens cap.

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

  Tables 1 to 3 show Examples (Samples Nos. 1 to 26) of the present invention and Comparative Examples (Samples Nos. 27 to 29).

  Each sample was prepared as follows. First, glass raw materials were prepared so as to have the respective compositions shown in the table, and were melted at 1500 ° C. for 2 hours using a platinum crucible. The obtained molten glass was poured onto a carbon plate, and after annealing, samples suitable for each measurement were prepared.

The obtained sample refractive index (nd), Abbe number ([nu] d), the partial dispersion ratio ([theta] g, F), and was measured coloring degree lambda _70. The results are shown in Tables 1 to 3.

  The refractive index was shown by a measured value with respect to a d line (587.6 nm) of a helium lamp.

  The Abbe number is calculated using the values of the refractive index of the d-line of the helium lamp and the refractive indices of the F-line (486.1 nm) and the C-line (656.3 nm) of the hydrogen lamp, and the Abbe number (νd) = ｛(nd) -1) / (nF-nC)}.

  The partial dispersion ratio is determined using the refractive index values of the F line, the C line, and the g line (435.8 nm) of the hydrogen lamp, and the partial dispersion ratio (θg, F) = ｎ (ng−nF) / (nF−nC ) Calculated from equation (1).

The degree of coloring λ ₇₀ was measured using a spectrophotometer at a wavelength of 200 to 800 nm at 0.5 nm intervals for optically polished samples having a thickness of 10 mm ± 0.1 mm. The evaluation was made based on the shortest wavelength showing a transmittance of 70% in the rate curve.

As is evident from Tables 1 to 3, No. 1 was an example of the present invention. Each of Samples 1 to 26 was vitrified without devitrification, and had a refractive index of 1.7992 to 1.8891; an Abbe number of 23.2 to 27.3; and a partial dispersion ratio of 0.5995 to 0.6180. , The degree of coloring λ ₇₀ was 415 to 445 nm, and had desired optical characteristics.

On the other hand, in Comparative Example No. 27 samples did not vitrify. No. Sample No. 28 had a high partial dispersion ratio of 0.6502. No. 29 samples of the coloring degree λ ₇₀ was as high as 500nm.

  The optical glass of the present invention can be used as a glass material for mold press molding or a glass material for polishing, as an optical pickup lens for CD, MD, DVD, and other various optical disk systems, a video camera, a digital camera, and a shooting lens or light for other general cameras. It is suitable for communication lenses and the like.

Claims (10)

In _{mol%, SiO 2 1.5~60%, B} 2 O 3 1~30%, Ta 2 O 5 0~15%, Nb 2 O 5 12~35%, TiO 2 0~15%, and Li ₂ O ₊ Na ₂ O ₊ K ₂ contain O 0.1 to 40%, and lead component, arsenic component, optical glass characterized in that it does not substantially contain fluorine component.   The optical glass according to claim 1, further comprising 0 to 10% of MgO + CaO + SrO + BaO + ZnO in mol%. The optical glass according to claim 1, further comprising 0 to 15% of ZrO _{2 and} 0 to 10% of Al ₂ O ₃ in mol%. Furthermore, La ₂ O ₃ + Gd ₂ O ₃ + Bi ₂ O ₃ + Y ₂ O ₃ + Yb ₂ O ₃ + TeO ₂ + GeO ₂ 0 to 10% is contained in mol%. The optical glass according to 1. In a molar _ratio, the optical glass according to claim 1, _{Nb 2 O 5 / Ta 2 O} 5 is characterized in that 350 or less. In a molar _ratio, the optical glass according to any one of claims 1 to 5 TiO 2 / _Nb 2 _{O 5} is characterized in that 1.2 or less.   The optical glass according to any one of claims 1 to 6, wherein a refractive index is 1.75 to 1.95 and an Abbe number is 15 to 35.   The optical glass according to any one of claims 1 to 7, wherein a partial dispersion ratio is 0.645 or less.   The partial dispersion ratio (θg, F) and Abbe number (νd) satisfy the relational expression of (θg, F) <− 0.0041 × (νd) +0.7190. An optical glass described in Crab. The optical glass according to any one of claims 1 to 9, wherein the coloring degree λ ₇₀ is less than 480 nm.